Combine the mayonnaise, chile blend, and lime juice in a mixing bowl.
Whisk well until combined. Season with salt to taste.
Preheat the grill over medium-high heat.
Slice the pineapple into ¼” rounds. Coat well with oil and season with a pinch of salt. Grill the pineapple until caramelized, about 4-5 minutes per side. Transfer the pineapple to a cutting board and let cool slightly.
Combine the sliced shallot, jalapeno, lime juice, and olive oil. Dice the pineapple and toss with the shallot mixture. Season with salt to taste.
Let sit and marinate while you grill the fish.
Grilled Fish Tacos
Combine the cabbage with about half of the chile mayo, or until generously coated. Toss well and set aside.
Brush off the grill and wipe the grates with a bit of oil. Coat the halibut with a generous amount of oil as well and season with salt. Grill the fish for about 3-5 minutes per side, or until just cooked through. *Do not flip the fish until it begins to release on one side.
Transfer the fish to a plate and use two forks to break it apart into pieces.
Grill the corn tortillas for a minute or so on each side until charred and crisp.
Assemble the tacos by placing some of the cabbage down onto the tortilla. Top with the fish, the pineapple salsa, a drizzle of the chile mayo, and a few cilantro leaves.