In a skillet over medium heat add the olive oil. After a minute add onions and saute for 2 minutes. Add garlic, salt and chili flakes, cook another minute. Stir in the tomatoes and bring to a simmer. Cover, turn heat to low and cook 5 minutes (start shrimp).
Shrimp
Peel and devein shrimp, rinse with water and pat dry. Toss with salt and pepper.
In a large skillet over high heat add the olive oil. After a minute add the shrimp and cook 1 minute per side. Deglaze pan with Ouzo (optional).
Spoon tomato sauce mixture over shrimp, add the herbs and feta cheese. Cover and cook on low for 2 minutes. Cheese should be melted. Serve immediately.