Tostadas are one of my favorite "healthy" meals. Sometimes I get complicated and make my own beans and tostada shells, but this time I opted for purchased shells, and beans from Compadre's (house-made, no lard).
You could also add any meat you want - pulled pork, shredded chicken, ground beef. Or skip the beans and top with ceviche. Endless possibilities. These particular tostadas were vegetarian out of laziness and lack of thawed protein.
There's no recipe, just spread some beans on the tostada shell, and top with whatever you want. This one had tomatoes, lettuce, avocado, cilantro, red onion, green olives, yellow chile, green chile sauce, Tapatio, and a squeeze of lime juice. (Yes, I have a tendency to over-chile.) No cheese, because I typically only use cheese when meat is a topping. But go ahead and use cheese if you want.
Visually appealing (look at all the colors!), always delicious. Great for when you don't feel like turning on the oven/stove. Lots of chopping, but worth it.