Pasta with Vodka Sauce

1 pound pasta
pinch of crushed red pepper flakes, or more to taste
1/2 cup vodka
4 tablespoons butter
1/4 red onion, sliced
2 tablespoons tomato paste
3/4 cup heavy cream
3/4 cup freshly grated Parmesan cheese
salt and pepper to taste

Bring a large pot of salted water to boil. Add the pasta and cook just until al dente. Drain. In a cup, steep the red pepper flakes in the vodka and set aside while you get on with making the sauce.

In a skillet, melt the butter and saute the onion over medium-high heat until golden and translucent, 5-8 minutes. Add the vodka and pepper flakes and simmer for 2 minutes. Stir in the tomato paste. Reduce the heat to low and add the cream and grated cheese. Stir well and heat thoroughly. Toss with the drained, cooked pasta.