Preheat oven to 350 degrees. Slice baguette diagonally into sixteen 1/2-inch-thick slices; brush both sides with a total of olive oil. Bake on a baking sheet until golden, about 8 minutes.
Halve avocado lengthwise and remove pit; scoop flesh into a small bowl. Mash with lemon juice; season with coarse salt and ground pepper. Spread on toasted bread; top with grape tomatoes.