Copycat Taco Bell Mexican Pizzas

Name: Copycat Taco Bell Mexican Pizzas
Ingredients: 8 (6 inch) corn tortillas; 2 tablespoons canola oil, divided; 3 tablespoons water; 1 teaspoon cornstarch; ¼ cup finely chopped yellow onion; 8 ounces 90%-lean ground beef; ½ teaspoon smoked paprika; ½ teaspoon garlic powder; ½ teaspoon onion powder; ½ teaspoon chili powder; ¼ teaspoon salt plus 1/8 teaspoon, divided; 1 (15 ounce) can no-salt-added black beans, undrained; ¼ cup salsa, plus more for garnish; ½ cup shredded Mexican 3-cheese blend; ¾ cup finely shredded iceberg lettuce; ¾ cup finely shredded red cabbage; ¼ cup thinly sliced radish; ½ cup halved cherry tomatoes; ¼ cup sliced scallions