This open-face melt makes the perfect weekend lunch -- just add a green salad.
Heat olive oil in a large skillet over medium heat. Add leeks and thyme; season with salt and pepper. Cook, stirring frequently, until leeks are very tender and just beginning to brown, 15 to 20 minutes.
Meanwhile, heat broiler with rack set 4 inches from heat. Arrange bread on a broilerproof baking sheet. Dividing evenly, layer bread with Brie, cooked leeks, and sliced tomatoes; drizzle with olive oil, and season with salt and pepper.
Broil until cheese has melted and tomatoes start to brown, 5 to 8 minutes. Serve immediately.