Add buttermilk, jalapeno, smoked paprika, 1/2 the lime juice, salt, and pepper to a large resealable zip top bag. Add the halibut and let marinate for 30 minutes.
Preheat the grill to medium-high heat.
Once hot, brush the grill grate with some olive oil. Remove the fish from the marinade and grill the fish 4 minutes per side, about 8 minutes total. Remove to a plate and break the fish into chunks. Sprinkle with lime juice and a touch more salt.
Grill corn tortillas until warm and soft and they have a few charred marks.
To assemble the tacos, place a nice spoonful of the fish onto the center of a warmed tortilla. Top with the Cabbage Slaw. Garnish with lime wedges and cilantro leaves.
Using a large holed grater attachment for a food processor, shred the cabbage and red onion. Add to a large serving bowl with the chopped cilantro.
Mix the sour cream, chipotle, lime juice, honey, salt, and pepper in a separate bowl.
Add the dressing to the grated cabbage. Allow the mixture to marinate for at least 30 minutes and up to 8 hours before serving