Heat the olive oil in a 26 cm / 10-inch Dutch oven over medium heat. Add the onion and bell pepper and cook for 5 to 6 minutes, until soft.
Add the garlic, smoked paprika, oregano, and red pepper flakes. Cook for 1 minute, until fragrant.
Stir in the tomato paste and cook for 1 minute to deepen its color.
Add the crushed tomatoes, butter beans, vegetable broth, bay leaf, salt, and black pepper. Stir well to combine.
Bring to a gentle boil, then lower the heat and simmer uncovered for 20 to 25 minutes, stirring occasionally, until the stew has thickened and coats the back of a spoon.
Remove the bay leaf. Taste and adjust the salt, since butter beans and broth can vary in saltiness by brand.
Stir in the lemon juice.
Ladle the stew into bowls. Top with crumbled feta and chopped parsley, and serve with crusty bread.