Melt butter in a large skillet over medium heat. Add garlic and cook, stirring often, for 1-2 minutes, until garlic just begins to brown. Remove garlic from the skillet with a slotted spoon, transfer to a small bowl or plate and set aside.
Add green beans and toss to coat with butter. Cook over medium heat, stirring often, for 3-4 minutes. It’s ok if the green beans begin to blister and brown in spots, but don’t let them burn.
Add the garlic back to the skillet with a ½ cup of water and continue to cook, stirring often, until water is evaporated and green beans are crisp tender.
Squeeze lemon juice from half a lemon over the beans and stir to incorporate. Season with salt and pepper to taste.
Grate fresh Parmesan over beans (if desired) and serve immediately.