1. Preheat oven to 400°F.
2. Put baguette rounds directly on oven rack and bake until toasted, but not browned, 2 to 3 minutes. Set aside.
3. Using a fork, mash avocado, lime, jalapeño, cilantro, scallion, garlic, goat cheese, oil, salt, and pepper in a small bowl.
4. Spread 1 to 2 teaspoons avocado mixture on each crostini and top with tomatoes.
TIP: Make these up to 1 hour ahead of time and keep covered at room temperature.