Weeknight Meat Sauce with Rigatoni (Pressure Cooker)

If you have never invested in a pressure cooker, you really should consider it.  The new models are so easy to use and take all the fear out of making a quick meal.  
This quick meat sauce with all the flavor of Bolognese, is cooked with the uncooked pasta and is ready is 5 minutes!

1 Tbsp. olive oil 1 medium onion, chopped Salt and Pepper 3 garlic cloves, minced 1/4 tsp. red pepper flakes 1 tsp. dried oregano 1 Tbsp. tomato paste 1 lb. 85% lean ground beef (or turkey) 3-1/2 cups water 1 (28-ounce) can San Marzano tomatoes (crushed by hand) 1 lb. rigatoni Chopped fresh basil Grated Parmesan or Romano cheese
Heat oil in pressure cooker on "Brown" setting.  Add onions and 1/4 teaspoon salt and cook until onions are softened and lightly browned.  Stir in garlic, pepper flakes, oregano and tomato paste and cook until fragrant, about 1 minute.  Stir in ground beef and cook, breaking up meat with wooden spoon, until jjno longer pink, about 3 minutes.  Stir in water, crushed tomatoes and pasta.
Lock pressure-cooker lid and cook on High Pressure for 5 minutes.   Let pressure come down naturally.  Stir and add salt and pepper to taste. Garnish with basil and cheese