Heat a medium saucepan over moderate heat for 1 minute. Pour in the olive oil and turn the heat down to low. Add the rosemary sprig and the crumbled chile. When the rosemary begins to sizzle, add the garlic. Cook for 1 minute or so, then add the lima beans and 1/2 teaspoon of salt. Stew gently for 5 to 7 minutes, until the limas are soft, but not mushy. Drain the beans, reserving the oil. Discard the rosemary sprig and chile.
Place the beans in a food processor and puree. With the machine on, slowly pour in some of the reserved oil and puree until smooth; you may not need all of the oil. Season with salt, pepper and a squeeze of lemon.