Boil pasta in a large pot of well-salted water until al dente. Reserve 3/4 cup water and drain.
Whisk ricotta, 1/2 cup Parmesan, lemon zest, lemon juice, salt, pepper, and red pepper flakes until smooth.
Warm 1 tbsp olive oil with butter in a skillet over medium heat. Sauté garlic until fragrant, about 30 seconds.
Toss drained pasta in the garlicky butter. Remove from heat and stir in ricotta mixture with splashes of pasta water.
Drizzle remaining olive oil, add herbs, and adjust with more lemon or water until silky.
Serve hot with extra Parmesan on top.