Fill a large pot halfway with water and add the shrimp with shells. Cook until just pink, about 3–4 minutes. Remove the shrimp, peel and devein them, and set aside while reserving the cooking broth.

Grate the three plantains and immediately mix them with about half a cup of the shrimp broth to keep them from browning.

In a medium pot, heat 1/4 cup of achiote oil over medium-low heat. Add the garlic and cook until fragrant, about 2 minutes.

Stir in the diced onion and bell peppers, season with salt, pepper, and ¼ teaspoon cumin, and cook for about 4 minutes until softened.

Add the grated plantain mixture and let it cook with the aromatics for about 2–3 minutes.

Begin stirring in the shrimp broth, one ladle at a time, making sure the mixture stays creamy. The plantains will absorb broth quickly, so continue adding liquid as needed. Stir often to avoid sticking.

Cook for 35–40 minutes, until the plantains are tender and the mixture has a smooth, porridge like texture. Once it reaches this consistency, stir the cooked shrimp back in and let them warm gently in the stew for just a few minutes so they stay tender and don’t overcook. Add an salt and pepper to taste here.

While the stew simmers, thinly slice one red onion and rinse under cold water. Drain well, then place in a bowl with the juice of 1–2 limes, chopped cilantro, salt, and pepper. Toss to combine and let rest to lightly pickle.

Mix fresh cilantro into the stew just before serving and adjust seasoning with salt and pepper.

Serve hot with white rice and top with pickled onions and extra cilantro.