A watery sauce usually means it hasn't simmered long enough, or that it never got to bond with the pasta. Both are easy to fix.
The fix right now
- Simmer it uncovered in the widest pan you have, so water evaporates faster.
- Finish the pasta in the sauce for the last 1 to 2 minutes, with a small splash of pasta water.
- Toss hard. Starch from the pasta thickens the sauce and helps it cling.
Why not add flour or lots of tomato paste?
Flour can make it taste chalky, and too much paste can overpower the sauce. Reducing it keeps the flavor clean and makes it stronger.
Common causes
- Draining the pasta until dry and spooning sauce on top.
- Rinsing the pasta, which washes off the starch.
- Leaving the lid on while it simmers.
- Using watery fresh tomatoes when they're out of season.
