Cook pasta according to package directions. Reserve 1/2 cup pasta water before draining.
Blend cottage cheese and reserved pasta water until completely smooth. Set aside.
Heat olive oil in a large skillet over medium heat. Add onion and cook 5–7 minutes until softened.
Add tomato paste and cook for 2–3 minutes, stirring frequently, until slightly caramelized.
Add vodka and cook for 2–3 minutes until mostly cooked off.
Reduce heat to low. Add blended cottage cheese, salt, red pepper flakes, and parmesan. Stir and cook 3–5 minutes until smooth and heated through.
Add drained pasta and toss to coat. Add pasta water as needed to adjust consistency.
Serve immediately with fresh parsley and extra parmesan.