Mix asparagus and onion with olive oil (with salt and pepper up to taste). Set everything into one large layer over a baking sheet. Oven bake at 450 °F (230 °C) for 10 minutes while stirring few times and turn vegetables once (until tenderness and lightly browned). Cool down and slice asparagus into thirds.
In a small bowl, mix tomatoes, jalapeno peppers and coriander (with salt and pepper up to taste). Set two tortillas over a small plate and equally divide vegetables over each tortilla. Add 30 ml (2 tablespoons) of tomatoes mix and gratin with two others tortillas over while pressing lightly. Oven bake at 450 °F (230 °C) for 8 to 10 minutes or until it browns. Slice into parts.
For the cumin and lime sour cream:
Mix sour cream, cumin and lime juice. Serve with tortillas and remaining tomatoes mixture.