Bring a large pot of heavily salted water to a boil. Meanwhile, finely chop 4 cloves garlic. Finely grate 1/2 ounce Parmesan cheese (about 1/4 packed cup), or measure out 1/3 cup store-bought grated. Pick fresh basil leaves and thinly slice until you have 1/4 cup.

Add 12 ounces dried bow tie pasta to the boiling water and cook according to package instructions until al dente, about 11 minutes. Meanwhile, heat 2 tablespoons olive oil in a large high-sided skillet over medium-high heat until shimmering. Add the garlic and 1/4 teaspoon red pepper flakes and cook, stirring, until the garlic is fragrant, about 30 seconds. Add 1 pint grape or small cherry tomatoes and cook, stirring occasionally, until the tomatoes burst, about 9 minutes. Remove the skillet from the heat if the pasta is not ready yet.

When the pasta is ready, reserve 1 cup of the pasta water. Drain the pasta.

Add 3 tablespoons tomato paste to the skillet and continue to cook, stirring occasionally, until the tomato paste darkens in color, about 2 minutes. Add 1 cup half-and-half, 1/2 cup of the reserved pasta water, Parmesan, and 1/2 teaspoon kosher salt. Bring to a simmer, stirring occasionally. Add the pasta and toss until coated and warmed through, about 2 minutes more. If the sauce is too thick, stir in more of the reserved pasta water 1 tablespoon at a time.

Remove the skillet from the heat. Add 1/4 cup sour cream and stir to combine. Taste and season with more kosher salt as needed. Serve topped generously with the basil, more Parmesan, and more red pepper flakes, if desired.