While meatballs are baking, heat 1 tbsp of olive oil in a medium-large saucepan over medium heat. Sauté 1/2 a diced onion until translucent, 3-5 minutes. Add 3 cloves of minced garlic and cook for another minute. Add basil, red pepper flakes, 1 tsp oregano, crushed tomatoes, tomato sauce, 1/4 tsp salt, and 1/4 tsp ground pepper. Bring to a boil and then reduce heat to simmer for 20 minutes, stirring occasionally.