Combine the minced cilantro, scallions, chili pepper, red onion, lime juice, and zest in a large bowl. Sprinkle lightly with salt and set aside.
Make the roasted potatoes:
Preheat oven to 425ºF.
Arrange the potatoes on a baking sheet and drizzle with 1 tablespoon oil. Sprinkle the garlic powder, paprika, and cayenne powder if using. Mix to coat well and arrange in an even layer. Transfer to the oven for 15 minutes.
After 15 minutes, remove the baking sheet from the oven and add the red bell pepper and red onion to the baking sheet. Drizzle with a teaspoon of neutral oil and sprinkle salt on top of the pepper and onion before mixing gently into the potatoes. Arrange in an even layer and return to the oven for 20–25 minutes. Turn off the heat and leave the baking sheet in the warm oven as you finish the rest of the recipe.
Cook the fish:
Add 1 tablespoon neutral oil to a large skillet over medium-high heat.
Pat the tilapia dry and season all over with salt and pepper.
Add the Wondra to a large bowl. Dip each tilapia filet in the Wondra and coat the fish evenly. Shake off any excess flour.
Transfer the fish to the hot skillet and cook in an even layer. Cook in batches if needed so as not to crowd the skillet. Fry until golden brown and crisp, about 3–5 minutes per side. As the filets reach 145ºF, transfer them to the bowl of minced herbs.
Once all the fish finishes cooking, use two forks to flake into the minced herbs and lime juice. Taste and adjust the seasonings.
To serve:
Pile the fish salpicón on top of tostada shells or charred tortillas and garnish with scallion greens, sliced cucumber, radishes, and guacamole or diced avocado if you like. Serve with the roasted potatoes on the side. Enjoy!