Preheat the oven to 450°F (230°C). Line a baking sheet with parchment paper or lightly oil it.
In a large bowl, toss the chicken tenders with 2 tablespoons brown rice flour, 1 teaspoon garlic powder, 1 teaspoon onion powder, and salt and black pepper to taste until evenly coated.
In a separate bowl, combine 3/4 cup brown rice flour, the shredded coconut, smoked paprika, ground turmeric, and lime zest. Stir to mix.
Add 3/4 cup buttermilk to the flour-coconut mixture and stir until a thick batter forms; add up to 1 cup total buttermilk if you need to loosen the batter. The batter should remain thick enough to coat the tenders.
Add the floured chicken to the batter and toss until each piece is well coated.
Arrange the coated tenders on the prepared baking sheet without overcrowding. Drizzle or brush a little olive oil over the pieces.
Bake for 10 minutes. Remove the tray from the oven and spoon any remaining batter from the bowl over the tenders, then drizzle a bit more olive oil.
Return to the oven and bake for another 15 minutes, or until the tenders are crisp and cooked through. Sprinkle with flaked sea salt before serving.
While the chicken bakes, make the sauce by whisking together 1/2 cup mayonnaise, 1/4 cup buffalo sauce, 1 tablespoon ketchup, and 1/2 teaspoon garlic powder until smooth.
Serve the crispy turmeric chicken tenders with the buffalo-mayo sauce.