Wash and trim broccoli, removing tough ends. Pat dry to remove all excess moisture.
Heat a cast iron skillet over medium-high heat. Add olive oil to heated skillet, followed by broccolini, placed in a single layer. Leave unmoved for 2-3 minutes to develop a char.
Once bottom side is charred, flip broccolini over and cook for another 2-3 minutes.
Reduce heat to medium-low. Add garlic and butter, tossing constantly for an additional 1-2 minutes until fragrant.
Season with salt and cracked black pepper then squeeze lemon juice over top to fully coat broccolini.
Transfer broccolini to service dish. Serve immediately.