Make the ravioli dough: Place the flour in a large bowl and make a well in the center. In a small bowl, whisk eggs, oil and water until frothy.
Pour the egg mixture into the well in the flour and, using a fork, gradually stir the flour from the sides of the well into the egg mixture until all the flour is moistened. Lightly flour your hands and knead the mixture until a rough ball of dough forms (if necessary, add a few drops of water or a pinch of flour until a ball forms).
Lightly dust a clean, dry work surface with flour. Spread the dough onto the surface and knead until smooth and elastic, about 5 minutes. (If the dough is too sticky, sprinkle lightly with flour; if it is very dry, add a few drops of water to moisten it.)
Transfer the dough to a lidded container – like a bowl with a plate placed on top – and let it rest at room temperature for at least 30 minutes and up to 1 hour (this helps loosen the gluten, making the dough more pliable and easier to deploy).
Prepare the beet-ricotta filling: Meanwhile, in a food processor, combine the ricotta, beets, parmesan, thyme, fine salt, garlic powder and a few grinds of pepper and blend for 15 seconds. Scrape the sides and bottom of the bowl and blend until completely and smooth, 20 to 30 seconds – be careful not to overwhip.
Assemble the ravioli: When the dough is ready, divide it into four equal pieces and place them all in a lidded container – each should weigh around 100 grams.
If using a pasta machine: Take a piece of dough and flatten it into a small rectangle; keep the other pieces of dough covered. Start with the widest setting (usually setting 1) and send the dough through the rollers twice (no need to fold the dough in between). Gently grab the bottom of the sheet as it passes, taking care not to pull or stretch the dough. Adjust the thickness setting of the pasta roller to the next narrowest setting and send the dough through the rollers twice again. Continue in the same way, feeding the dough twice through each thickness setting, until you have a very thin, translucent sheet (usually the penultimate setting on the machine). Lightly sprinkle the semolina sheet if it starts to become sticky. Each sheet should measure approximately 22 x 5 inches. When finished, generously dust both sides of the pasta sheet with semolina flour and fold it in half, then place it on a baking tray and cover with a clean, dry tea towel. Repeat with remaining dough.
If you are rolling out the dough sheets by hand: Take a piece of dough and flatten it into a small rectangle; keep the other pieces of dough covered. Lightly sprinkle a clean, dry work surface with semolina. Roll out the dough into a translucent rectangle measuring 22 x 5 inches. If the dough starts to stick, dust lightly with semolina flour as you roll. When rolling out the dough by hand, the dough rectangles may be narrow around the edges – that’s okay. When finished, generously dust both sides of the pasta sheet with semolina flour, fold it in half, then place it on a large baking sheet. (You can also place the pasta sheets on a clean, dry counter.) Cover with a clean, dry kitchen towel. Repeat with remaining dough.
Lightly sprinkle a clean, dry work surface with semolina. Place two large baking sheets near your workspace.
Place a sheet of pasta on the surface and dust off excess flour (keep remaining pasta sheets covered). Use a pizza cutter or paring knife to square off the ends of the rectangle (the ends may become narrower than the middle). Fold the sheet in half lengthwise, then unfold it to create a center crease. Place a small bowl of water near your work space.
Arrange the sheet of pasta so that it is horizontal to you and, using two spoons, add 1/2 tablespoon of filling to the bottom half of the sheet, starting at 1/ 2 inch from the edge and leaving about 1 inch between each spoon. (measure the amount of filling the first time, then you can approximate it for future spoonfuls). Make a single row of 8 to 10 spoonfuls total, using the center line as a guide. Use a pastry brush or your finger to lightly apply water to the top half to moisten it, then carefully fold it over the filling. Use your fingers to gently press the top fold to seal the top, then between each filling to seal the sides, then on the bottom to seal the bottom, removing as much air as possible. Use a fluted pasta cutter, pizza cutter, or paring knife to separate the sheet of dough into individual squares. (If desired, cut a thin line across the top and bottom with a fluted cookie cutter to have even edges).
Repeat with the remaining dough, placing the filled and sealed ravioli on the baking sheets. (If serving 2 people, transfer half of the ravioli (16) to a small plate and freeze for 30 minutes; then transfer to an airtight bag or container and freeze for another meal.)
Cook the ravioli: Bring a large pot of water to a boil over high heat. Add enough salt so that the water is slightly salty. Add 16 ravioli and boil until tender and cooked through, about 3 minutes. Using a slotted spoon or spider, then carefully transfer to a colander to drain excess water. Reserve 1 cup of the pasta cooking water and discard the rest. Transfer the drained ravioli to a serving dish. Repeat and boil the remaining ravioli.
Prepare the garlic butter sauce: While the ravioli cooks, in a large skillet over medium heat, melt the butter. Add garlic and cook until fragrant and golden, about 30 seconds. Add the reserved pasta water, bring to a vigorous boil, and cook until the sauce is slightly thickened and glossy, 2 to 3 minutes. Stir in thyme and cook until thickened and saucy, about 1 minute more. Remove from the heat and pour the sauce over the ravioli. Sprinkle more thyme, grated Parmesan and flaky salt over the ravioli and serve immediately.