Caramelize the onions - To a skillet over medium-high heat with a drizzle of olive oil, add the thin-sliced onions. Add a few grinds of sea salt (about ¼ teaspoon). If I'm in a hurry, I leave the heat at medium-high, and keep a close eye on the onions, stirring often. When the onions are mostly brown and quite soft, they're done. You can remove them to a prep bowl until ready to serve.
Make the charred corn - Add about a teaspoon of oil to a skillet over high heat. Add the corn kernels. Cook until you see some nice charred spots on the corn, stirring occasionally. Season with salt and pepper, remove from the pan, and set aside.
Make the nopalitos and red chile sauce - With either a drizzle of oil or some cooking spray, add the diced nopalitos to a skillet on medium-high heat. Sauté until the mucilaginous liquid evaporates, stirring occasionally. This process usually takes 7 to 10 minutes. Stir the red chile sauce into the nopalitos over medium-high heat. Bring up to a boil, then reduce to a simmer. Add broth or water to thin if needed. Cover and simmer until ready to serve. It only needs to be heated throughout.
To serve - Fill warm corn tortillas with a scoop of nopalitos and red chile sauce, top with caramelized onion, charred corn, and fresh toppings. Delicioso!