1. Warm 1 Tbsp. oil in a large saucepan over medium-high heat. Add garlic and cook, stirring, until fragrant, about 30 seconds. Stir in tomatoes, thyme and 1/2 tsp. salt. Bring to a simmer, reduce heat to medium-low and cook until slightly thickened, about 10 minutes. Stir in olives.
2. Sprinkle tilapia with salt and place on top of tomato sauce. Cover and cook until fish is opaque throughout, 8 to 10 minutes. Drizzle with remaining 2 Tbsp. olive oil, sprinkle with parsley, and serve.