Heat 2 tablespoons butter in a large skillet over medium-high heat until foaming, about 1 minute.

Add green beans in a single layer, season with salt and pepper, and cook without stirring for 4 minutes until they begin to blister and brown.

Stir and cook for another 3–4 minutes until tender-crisp and lightly charred.

Push green beans to the sides of the pan. Add remaining 1 tablespoon butter and minced garlic to the center, cook for 30 seconds until fragrant.

Scatter panko over the green beans and garlic, toss gently to coat, and cook for 2 minutes until the breadcrumbs are golden.

Squeeze half the lemon over everything, toss once more, and serve immediately.