Preheat the oven to 220°C (425°F).
Rinse and place the cherry tomatoes in an ovenproof dish. Add the olive oil, balsamic vinegar, Herbes de Provence, salt, and pepper. Mix well to coat the tomatoes. Bake for 25 minutes, until the tomatoes burst and soften. Stir the tomatoes once they're halfway cooked.
Meanwhile, lightly toast the bread slices. Peel and slice the avocado. Chop the basil.
Start by spreading half of the Janis cheese (¼ block) on the toasted bread slices. Add the avocado slices, the roasted cherry tomatoes, and crumble the remaining Janis cheese on top.
Using a spoon, scoop the caramelized juices from the tomatoes remaining in the bottom of the dish and drizzle them over the toasts. Add a drizzle of olive oil, the basil, a few seeds, and a pinch of fleur de sel.