Preheat the oven to 375° F.
Warm olive oil in a skillet. Add the sliced garlic and cook on low heat for 2 minutes so the oil is flavored. Add the tomatoes and chili flakes, turn up the heat and cook for about 3 minutes. The tomatoes should pop, blister and burst. Season with salt and pepper. Take it off the heat.
Transfer the tomatoes along with the juices and oil to a small oven proof ceramic dish or cast iron dish. Sprinkle the thinly sliced onions and olives. Place the feta on top of the tomatoes.
Bake, uncovered, for 20-25 minutes, until the feta is soft and bubbly. Turn broiler to HIGH, and broil for 2 minutes if you like the cheese slightly browned. Garnish with chopped basil or parsley.
Serve with toasted bread or spooned over roasted vegetables, fish or chicken.
Serves 3-4 as a side dish and 6 as an appetizer.