If you haven't already, make our walnut gremolata.
Bring a large pot of salted water to a rapid boil. Add pasta, then cook according to package directions until al dente. Before draining, reserve cooking water.
Heat olive oil and unsalted butter in a large skillet over medium-high heat. When hot, add sliced garlic cloves, anchovy fillets, and crushed red pepper flakes, then cook. Be careful, this will splatter! Use a spatula to help break up the anchovy fillets, which will dissolve in the oil.
Add the drained pasta along with reserved pasta water and the juice of 1 lemon. Add ricotta cheese and grated Parmesan cheese. Stir until thoroughly mixed and the ricotta has melted, adding more pasta water as needed to thin out the sauce. Taste, adjust seasoning.
Take the remaining ½ cup ricotta cheese and spread it on the bottom of a large bowl or serving tray. Pour the lemon pasta and sauce directly on top, then garnish with walnut gremolata. Give the entire dish a little sprinkle of flaky sea salt, then serve immediately with fresh cracked black pepper!