To make the tostadas, lay tortillas out on a large sheet pan. Cover both sides with a light mist of cooking spray and the lightest sprinkle of kosher salt. Bake at 400 degrees F for 5 minutes, then flip and bake for another 5-10 minutes, until they are fully crisp. Set aside.
While the tostadas bake, start the pinto beans. Warm oil in a medium saucepan over medium-high heat. When shimmering, add the garlic and cook for 30-60 seconds, just until fragrant. Stir in the pinto beans, 1/4 cup of the broth, cumin, salt, and all three chili powders. Reduce heat to the lowest setting and let simmer, adding extra broth a little bit at a time as needed if the beans become dry. Add lime juice just prior to serving.
While the beans simmer, make the salsa. Melt butter in a large skillet over medium-high heat. Add garlic, jalapeno if using, and chili powder. Cook until fragrant, about 1 minute.
Add corn kernels and ancho sauce. Stir to coat, then let the corn cook for about 5 minutes, stirring occasionally. Remove the skillet from the heat. Stir in tomatoes, Cotija, lime juice, and salt. Taste and add more salt as desired.
To assemble, mash a few slices of avocado on top of each tostada, then top with beans, corn, and other toppings as desired. I like a little extra lettuce or shredded cabbage and more lime. Enjoy!