Bring 4 quarts of salted water to a rolling boil with 1 tablespoon salt. Add penne and cook for 1 minute less than package directions, usually 9-10 minutes for al dente. Drain the pasta and reserve ½ cup of the pasta water.
1 lb penne pasta
Heat 2 tablespoons olive oil in a large skillet over medium heat. Add diced onion and cook 4-5 minutes until soft and translucent. Stir in minced garlic and cook 1 minute until fragrant, avoiding browning.
1 medium onion, 3 cloves garlic, 2 tablespoons olive oil
Pour in ¼ cup vodka and let it simmer on medium heat for 3-5 minutes until the alcohol smell fades and the sauce smells mellow and slightly sweet.
0.25 cup vodka
Stir in 28 oz tomato puree, ½ teaspoon red pepper flakes if using, and season with salt and pepper. Simmer uncovered for 10-15 minutes, stirring occasionally, until sauce thickens and coats the back of a spoon.
28 oz tomato puree, 0.5 teaspoon red pepper flakes
Remove the skillet from heat and stir in 1 cup heavy cream until smooth and pink. Add drained penne and toss to coat. Adjust thickness by adding reserved pasta water 2 tablespoons at a time if necessary. Stir in grated parmesan off heat until melted.
1 lb penne pasta, 1 cup heavy cream, 0.5 cup parmesan cheese
