In a large paella pan or wide, shallow skillet, heat the olive oil over medium heat.
Add the chopped onion and diced red bell pepper. Sauté for about 5 minutes until softened.
Add the minced garlic and cook for another 1 minute until fragrant.
Stir in the rice, smoked paprika, saffron threads, and cayenne pepper. Cook for 2 minutes, stirring frequently to coat the rice with the spices and oil.
Pour in the white wine and cook until it has mostly evaporated, about 2 minutes.
Add the seafood stock and chopped tomato. Stir gently to combine and bring to a simmer.
Reduce the heat to medium-low and cook the rice uncovered for about 15 minutes, without stirring, allowing the rice to absorb the liquid.
Arrange the shrimp, mussels, clams, and squid rings evenly over the rice. Sprinkle the peas on top.
Cover the pan with a lid or aluminum foil and cook for an additional 10-15 minutes until the seafood is cooked through, the mussels and clams have opened, and the rice is tender. Discard any unopened shellfish.
Season with salt and freshly ground black pepper to taste.
Remove the pan from heat and let it rest covered for 5 minutes.
Garnish with chopped fresh parsley and lemon wedges before serving.