Light up the grill (or a panini grill) and cook the pineapple, bell pepper, onion, and jalapeno over medium/high heat until slightly charred, 5 to 10 minutes. (Can skip this step if in a crunch for time)
Cover and refrigerate until chilled, about 1 hour. (Again, you can skip this step if needed)
For major yums, add this salsa to these Crispy Baked Avocado Tacos!