Add the bacon and onion to a large skillet over medium heat. Cook, stirring, until the bacon is beginning to crisp and the onions are golden, 5 to 7 minutes.
Increase the heat to medium high and add the green beans and tomato paste. Stir and allow to cook for a minute or two. Add the tomatoes, crushing them with your hands as you add them. Stir to combine. Season with salt, pepper and cayenne. Bring the mixture to a simmer and simmer until thickened and the beans are soft but still green, 5 to 7 minutes.