Clean the shellfish thoroughly with plenty of water to remove any sand residue.
Chop the vegetables into small cubes and mince garlic cloves. Set them aside.
In a paella pan, heat olive oil over medium heat. Sauté the onion, garlic and bell pepper until the onion is translucent.
Add the diced tomatoes. Season with a little salt.
Add the squid, followed by the mussels and clams. Let them cook for a few minutes. You'll notice that a broth begins to form—this is a good sign.
Add the rice and stir to mix everything together. Let the rice "nacar" (become translucent) for about 2-3 minutes. Then, add 4 cups of broth. Stir well. Add a teaspoon of saffron threads or powder and let it boil for about 3 minutes.
While there is still liquid in the paella pan, add the shrimp and the finely chopped parsley. Check the saltiness and adjust if necessary.
Let it cook until the liquid is almost completely absorbed. Key point: Do not stir so the socarrat (crispy bottom) can form.
Lower the heat and cover. Let it cook for 15 minutes and taste the rice. If it’s done, remove it from the heat and serve your seafood paella with a drizzle of olive oil on top for extra flavor.
Before serving, garnish with chopped parsley and lemon wedges.