Step 1Preheat the oven to 425 degrees, In a small bowl, mix together the brown sugar, kosher salt, ancho chili powder, regular chili powder, garlic powder, onion powder, and black pepper.
Step 2Brush the salmon with olive oil. Sprinkle with the spice mixture and rub to cover the salmon with the spice rub. Place the salmon on a baking sheet covered with foil. Bake for 8-10 minutes for thinner fillets, 12-16 minutes for medium thick fillets, and 18-22 minutes for thick fillets. Salmon is ready when it reaches about 145 degrees.
Step 3To make tostadas: Place the tortillas on a baking sheet or directly on the oven rack. Cook for about 4 minutes on each side until they are crispy. You can cook these at the same time as the salmon or make them while you prep the salmon.