In a food processor or blender, combine the coconut milk, almonds, onion, ginger, turmeric, lemon grass, and 1/4 teaspoon of salt. Process until smooth.
Heat a large non-stick skillet over medium-high heat. Season the fish fillets with salt and pepper on both sides, then place them skin-side up in the skillet. Pour the pureed sauce over the fish. Use a spatula to coat the fish evenly with the sauce. Sprinkle with red pepper flakes.
Reduce heat to medium, cover, and simmer for about 15 minutes, until the puree is thickened and fish flakes easily with a fork.