In a large heavy saucepan, heat the olive oil over medium-high heat. Add the onions and cook until translucent, about 3 minutes. Add the tomatoes and bell pepper and cook for 3 minutes. Add the shrimp and cook for 3 minutes. Stir in the tomato puree, oregano, bay leaf, and smoked paprika. Cook for another 3 minutes. Season with salt and pepper, to taste. Remove the pan from the heat and set aside. Remove the bay leaf and discard.
Heat a large heavy skillet over medium-high heat. Lay 2 tortillas, flat on the bottom of the pan, side by side. Put a small mound of cheese on 1 side of each tortilla. Wait until the cheese melts slightly, about 1 minute, and then add about 2 tablespoons of the shrimp mixture to each tortilla. Fold the tortillas over into half-moon shapes and cook to melt the cheese completely, another 1 to 2 minutes. Transfer to a platter and keep warm.
Repeat with the remaining tortillas, cheese, and shrimp mixture. Arrange the tacos on a serving platter and serve with lime wedges and hot sauce on the side.
*Cook's Note: Use only the outer part of the tomatoes without seeds.