Brush the oil on one side of the tortilla and place the tortilla (oiled side down) onto a baking sheet; spread the hummus in an even layer on top.
Add the spinach to a medium-sized skillet over medium heat with the water, salt, and pepper. Cook until the water evaporates and the spinach wilts, about 1 minute, stirring constantly. Spread the spinach on top of the hummus, and then sprinkle on the cheese.
Bake until the cheese is melted and the tostada is warm throughout, about 8 minutes.
When the tostada is almost finished cooking, cook the egg however you want (I did sunny-side up!).
Place the egg on top of the tostada and serve immediately.
Recipe by An Edible Mosaicâ„¢ at https://www.anediblemosaic.com/breakfast-tostada-with-spinach-hummus/