Gluten-Free Vegetarian Sandwich

Name: Gluten-Free Vegetarian Sandwich
Prep time: 10 min
Cook time: 25 min
Total time: 35 min
Cuisine: French
Ingredients: 250 g eggplant (thinly sliced); 250 g cherry tomatoes (halved); 30 g olive oil; 2 g salt; 2 g basil (ground dried); 1 g black pepper; 300 g onions (thinly sliced); 15 g olive oil; 1 g salt; 250 g crème fraîche (plant-based, gluten-free); 2 g black pepper (freshly ground); 500 g sandwich bread (gluten-free, 8 slices); 2 avocados (large)