Heat a large skillet over medium-high heat, then add olive oil. Sear green beans in a single layer until blistered and bright green, about 6 to 7 minutes total.

Push beans aside, add butter and garlic, cooking the garlic for 30 seconds until pale gold, then toss everything together and season with salt and pepper.

Remove from heat, add lemon juice and red pepper flakes, toss again, and transfer to a serving dish immediately.