Preheat oven to 500.

Im a large shallow baking pan, toss asparagus with 1 1/2 t oil and salt and pepper to taste until coated well. In another shallow pan, toss onion in similar manner. Roast vegetables in upper and lower thirds of oven, shaking pans ocassionally and switching position of pans in oven halfway through baking, until tender and lightly browned, about 10 minutes. Remove from heat.

Adjust oven to Broil. On a large baking sheet. Arrange 4 tortillas in one layer and divide vegetables, cheese and cilantro among them. Cover with remaining 4 tortillas.

Brush top of tortillas with remaining 2T oil and broil quesadillas about 3 inches from heat until golden, about 2 minutes. Turn quesadillas with a spatula and broil other side til golden brown.

Mix lime cream ingredients while quesadillas broil. Serve with quesadillas