For the beet salsa: Add beets, pineapple, red onion, lime juice, oil, salt, serrano and cilantro to a large bowl. Fold to combine. Taste and season as necessary.
For the pink mayo: Add sour cream, mayonnaise, chipotles, lime juice, sugar and salt to a blender and blend until smooth and combined.
For the fish: Preheat oil in a deep-fryer to 360 degrees F.
Add flour, cornstarch, baking powder, baking soda, salt and 1 1/2 cups water to a medium bowl. Whisk to combine.
Working in batches, dip strips of snapper into the batter and immediately into the fryer, being careful not to overcrowd the fryer. Fry, turning once, until golden brown and crispy on all sides, about 4 minutes. Remove to a paper towel lined plate to drain and sprinkle with salt. Serve 1 to 2 pieces of fish on a tortilla. Top with beet salsa and pink mayo.