Heat the olive oil in a 5-quart / 4.7 L Dutch oven over medium heat. Add the onion, carrots, and celery and cook for 6 to 7 minutes, stirring often, until softened.
Add the garlic, smoked paprika, and red pepper flakes. Cook for 1 minute, stirring constantly, until fragrant.
Stir in the diced tomatoes, vegetable broth, drained butter beans, and bay leaf. Bring the pot to a simmer.
Reduce the heat to medium-low, partially cover, and simmer for 15 to 18 minutes until the vegetables are tender and the broth has reduced slightly.
Uncover and stir in the kale in batches, letting each addition wilt down before adding more. Simmer for 3 to 5 minutes until the kale is wilted but still bright green.
Remove the bay leaf. Stir in the lemon juice, then season with salt and pepper to taste.
Ladle into bowls and top with grated parmesan. Serve with crusty bread on the side.