Hidden Veggie Pasta Sauce (Great for Picky Eaters!)

Name: Hidden Veggie Pasta Sauce (Great for Picky Eaters!)
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 small zucchini, (roughly chopped); 1 medium carrot, (roughly chopped); 1/2 leek, (approximately 1/2 cup, roughly chopped); 1/2 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; salt and pepper to taste