I am new to cooking, would like to make a tart using 3 cheeses, gruyere, gouda & asiago. Can anyone provide a receipe?

Google gruyere and carmelized onion tart. There are many versions out there. Keep the same amount of cheese, but make it a mixture of the 3. I would have a larger proportion of gruyere because it is milder, but that is just my personal taste.
You could also try a recipe for asparagus and gruyere tarts and do the same.