In a bowl, mix sliced onion, hot peppers, salt, vinegar, and warm water for the curtido. Stir gently and set aside to rest for at least 20 minutes.

Heat a pan over medium heat and sauté chopped onion until soft. Add fish, garlic powder, black pepper, and all-purpose seasoning. Cook gently, stirring until combined. Remove from heat and let cool.

In a large bowl, mix masa harina, baking powder, and salt. Stir achiote into warm water, then slowly add to the dry mixture. Knead until soft and smooth.

Divide dough into small balls. Flatten each into a circle, add a spoonful of filling, fold into a half-moon, and press edges to seal.

Heat oil in a deep pan over medium heat. Fry panades in batches for about 3 minutes per side until golden and crispy.

Remove panades with a slotted spoon and drain briefly. Serve hot with curtido spooned inside.