Simmer uncovered to evaporate excess liquid
Cook longer over low to medium heat
Add tomato paste
Stir in a cornstarch slurry
Mix in a flour slurry
Add a small amount of mashed potatoes
Blend in cooked onions or carrots
Use less water or stock next time
Add grated cheese
Stir in a roux
Puree some of the sauce ingredients
Add breadcrumbs
Use arrowroot slurry
Add a small amount of chia seeds
Let the sauce rest to thicken after cooking