Preheat oven to 180C. Brush a 20cm x 30cm baking tin with 1 teaspoon of the olive oil. Heat a frying pan over medium heat, add remaining oil and stir-fry onion for 2-3 minutes.
Arrange asparagus spears on bottom of tin, top with onions, semi-dried tomatoes and cheese. Combine eggs with a little salt and pepper and pour mixture over.
Bake until set and lightly browned, about 30 minutes. Allow to rest for 10 minutes before slicing.
Cut into small squares for a starter or snack, or cut into wedges for a light meal.