Preheat oven to 425°F. Lay tortillas on a cookie sheet in a single layer (do not overlap). Brush both sides of each tortilla with the canola oil. Bake 8-10 minutes, flipping halfway through cooking time.*
Prepare another baking sheet with nonstick spray, lightly brushing with oil, or parchment paper. Place salmon on the baking sheet, blot dry with a paper towel, and then rub spice blend on all sides.
Once tostada shells are finished, lower oven heat to 400ºF. Bake salmon for ~10 minutes per inch of thickness or until it flakes easily when tested with a fork or internal temperature reaches 145ºF. Allow to cool slightly, then flake fish into small pieces.
While shells and/or fish is cooking, place beans and salsa in a small saucepan and cook over medium heat until mixture begins to simmer and beans are heated through, stirring occasionally. Turn off heat and use a fork or potato masher to mash beans to the consistency of refried beans.** Add salt & pepper to taste.
Build tostadas by spreading a layer of beans on each shell. Top with flaked salmon, shredded romaine, tomatoes, avocado, and cilantro. Add additional garnishes to taste. Enjoy!