Kid-Requested Easy Hidden Veggie Pasta Sauce

Name: Kid-Requested Easy Hidden Veggie Pasta Sauce
Prep time: 10 min
Cook time: 30 min
Total time: 40 min
Cuisine: American
Ingredients: 1 tbsp olive oil; 1/2 medium onion, (roughly chopped); 2 cloves garlic, (minced); 1/3 cup zucchini, (roughly chopped); 1/3 cup carrot, (roughly chopped); 1/4 cup leek, (approximately 1/2 cup, roughly chopped); 1/4 cup red bell pepper, (cored and roughly chopped); 1 28 oz can crushed tomatoes; 1-2 cups of water, veggie or chicken stock; 1 tbsp tomato puree; 2 tsp Italian herb mix; 2 tbsp butter ((optional)); 1-2 tbsp sugar or maple syrup ((optional)); 1 tsp balsamic vinegar ((optional)); salt and pepper to taste