Cook the pasta in boiling salted water until they are al dente.
Make the sauce. Drain the silken tofu. Add the it to a blender with water, white miso paste, onion powder, and smoked paprika. Blend until perfectly smooth.
Heat it. Transfer the mixture to a saucepan and bring it to a boil. Dissolve the cornstarch in a tiny bit of water and add it to the sauce. Reduce heat to medium and whisk continuously until the sauce thickens.
Toss the drained pasta in the sauce and serve with freshly cracked black pepper.
Notes
Do not make this sauce with firm tofu or you won't get that silk-smooth consistency.
If you have kala namak (black salt) at home, you can add a pinch to the thickened sauce at the very end to give it a subtle eggy flavor.
You can store leftover sauce or leftover spaghetti tossed in sauce in an airtight container for up to 2 days in the refrigerator. Before serving, reheat it in a saucepan over low heat or in the microwave.