In a large pot, heat the olive oil over medium-low heat. Stir in the onion, salt, black pepper, red pepper flakes, oregano, thyme and smoked paprika. Saute for 5-6 minutes, or until onion is tender and translucent. Stir in the garlic and tomato paste, cooking for 2-3 minutes or until tomato paste starts to shimmer and look golden in spots, stirring constantly.
Stir in the crushed tomatoes and vegetable broth. Bring to a boil and then lower heat to a simmer. Cook for 20 minutes, stirring every five minutes or so and making sure to scrape the bottom of the pan. Stir in the kale leaves and cook until wilted, 2-3 minutes. Stir in the heavy cream. Season to taste with salt and black pepper.
Divide the soup among 4 bowls and top evenly with pistachios and a brown butter drizzle.