Preheat your charcoal or gas grill to a medium-low heat, positioning the rack about 4 inches from the heat source. 2.
Brush the pineapple and onion slices with olive oil. If you're concerned about them falling through the grate, thread them onto pre-soaked wooden skewers. 3.
Grill for about 8 minutes total, turning once or twice, until the pineapple and onion are soft and slightly charred. 4.
Remove the slices from the grill as they finish cooking.
Once cool enough to handle, discard the skewers (if used) and chop everything into bite-sized chunks, making sure to save as much of the juice as possible. 5.
In a medium bowl, combine the chopped pineapple and onion with the minced chile, lemongrass, fresh basil or mint, and lime juice. 6.
Sprinkle with salt and pepper and stir to combine.
Let the salsa sit for at least 5 minutes to allow the flavors to meld. 7.
Taste and adjust the seasoning, adding more chile for heat, lime for tang, or salt to enhance the flavors before serving.