Slice baguette on a slight diagonal about 1/3 inch thick; reserve ends for another use. Arrange slices on racks on two baking sheets (each 12 by 15 in.). Brush tops lightly with 2 tablespoons olive oil. Bake in a 425° regular or convection oven until lightly browned, 5 to 8 minutes.
Meanwhile, rinse, stem, and core tomatoes. Cut in half crosswise and squeeze out and discard seeds; chop tomatoes. (If not serving immediately, put tomatoes in a strainer or colander to drain.)
In a bowl, mix remaining 3 tablespoons olive oil, the lemon juice, and mustard. Stir in tomatoes, olives, basil, and garlic. Add salt and pepper to taste.
Spread cheese over one side of each slice of toast. Mound tomato mixture equally on top. Serve at once.
Nutritional analysis per piece.