Clean, devein and rinse shrimp, then set aside on paper towel to dry.
Cut the onion into square pieces. Wash and slice the sweet mini peppers and jalapeño, removing the core and seeds (keep the jalapeño seeds for a spicier dish.)
Mix cornstarch with salt and pepper, then toss the shrimp in the cornstarch mixture. Place the coated shrimp on a tray or plate without touching each other.
Heat the oil in a wok or cast iron skillet and bring to high heat. Sear the shrimp quickly about a minute on each side (when they are pink half way through, turn them over), then remove from the pan and place into a dish.
Keeping the heat high, add more oil if needed, then toss in the onion. Sprinkle in salt, then stir fry for one or two minutes, as it should not be soft or brown when ready. Remove and place in a small bowl.
Next, add the sweet mini peppers and jalapeño slices with a sprinkle of salt. Again, sear quickly, just for a minute or two, then add the onion again.
Toss the shrimp back into the pan with the onion and peppers, and stir to reheat. Adjust the heat and add more oil if needed.
Once the salt and pepper shrimp is hot, dinner is ready!