Preheat oven to 350F/175C.

If making your own crust, pre-cook the base as you would normally. (See link to other quiche recipe for my favorite version, which includes pre-cooking instructions.)

Dice the onion, warm the oil in a medium skillet over a medium heat then cook the onion until soft and lightly browned. Set aside.

Trim the ends off the asparagus and break or cut the stems in half.

Once the base is pre-cooked, put the cooked onions across the bottom of the crust. Arrange the asparagus on top - I put a layer of the lower stem then a layer of the top since you will see the top ones, arranged in a circle, but as you find easiest.

Put the tomatoes in between gaps in the asparagus so they are spread across the quiche. Sprinkle the gruyere over the top.

Whisk together the eggs, milk and a little salt and pepper. Carefully pour the mixture over the filling. Top with a little parmesan then bake for approx 30 minutes until set and lightly browned on top.