Simmer the sauce uncovered to let excess liquid evaporate
Add tomato paste and stir until fully incorporated
Mix in a cornstarch slurry and cook until thickened
Stir in a flour slurry and simmer briefly
Add grated cheese such as Parmesan
Blend in cooked vegetables like onions, carrots, or peppers
Puree part of the sauce to create a thicker texture
Add a small amount of mashed potatoes or potato flakes
Stir in breadcrumbs a little at a time
Add cream, mascarpone, or cream cheese for a richer, thicker sauce
Use less water or broth next time
Cook pasta directly in the sauce to absorb extra liquid
Add a roux made from butter and flour
Reduce the sauce over low to medium heat while stirring occasionally