Preheat the oven to 450 degrees F.
Remove any spines on the nopales by running a sharp paring knife against the grain of the spines. Place the cleaned nopal paddles on a baking sheet and roast until all the viscosity is absorbed back into the paddles, 20 minutes, flipping over once halfway through (if the nopales are thick, they may need more baking time). Cool completely, 30 minutes, before slicing into thin strips.
Combine the cooked nopales with the olive oil, lime juice, tomatoes, chiles, cilantro and onions in a non-reactive bowl and toss well. Season with salt and serve slightly chilled.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.