Step 1

Preheat the oven to 375°F. Grease a 13 x 9-inch baking dish; set aside.

Step 2

Cook the pasta in a large pot of well-salted boiling water for about 1 minute less than the package directions for al dente (about 9 minutes). Drain; return pasta to the pot.

Step 3

Stir in the marinara sauce and sour cream. Taste and season with salt and pepper.

Step 4

Transfer the pasta mixture to the prepared baking dish.

Step 5

Top with mozzarella and Parmesan.

Step 6

In a small bowl, stir together the breadcrumbs, melted butter, and garlic powder. Sprinkle over the top of the casserole.

Step 7

Bake, uncovered, for about 20-25 minutes, until golden brown on top and bubbly. If the topping starts to get too dark before the casserole is heated through, just tent the dish loosely with foil.

Step 8

Let stand for 5-10 minutes before serving. Garnish with crushed red pepper flakes, chopped fresh herbs, and extra Parmesan cheese if desired.