To make the salsa: Stir the tomatoes, onion, and cilantro together in a small bowl. Stir in the lime juice, olive oil and chile. Season with salt and pepper, to taste. Place in the refrigerator to chill while preparing the fish.
Preheat the oven to 200 degrees F.
Pour enough canola oil into a large frying pan to generously coat the bottom. Heat over medium-high heat until hot but not smoking.
While the oil is heating, season as many of the fillets as will fit in the pan comfortably with salt and pepper. Dredge the seasoned fillets in flour to coat both sides and shake off the excess flour. Carefully slip the coated snapper into the hot oil and give the pan a little shake to prevent sticking. Cook until lightly golden on the underside side, about 3 minutes. Flip the fillets over and cook until the thickest part of the fillets are opaque at the center, 2 to 3 minutes. Transfer to a baking sheet and keep warm in the oven. Repeat with the remaining fillets, adding more oil to the pan, if necessary.
Serve warm, passing the tomato salsa separately.
The type and amount of chile you add to the tomato-onion mix is up to you: choose a milder chile, like serrano or jalapeno and remove the seeds before mincing for a milder result. Pick a fiery chile like Scotch bonnet or habanero and leave the seeds in for lots of fire.