Bring some water to a simmer in a medium pot and set a steamer insert over it. Prepare an ice water bath. Add the broccoli to the steamer insert, cover and steam until al dente, about 5 minutes. Carefully remove the broccoli and plunge into the icy water. Let cool completely before removing it from the water. Pat dry and then set aside.
In a large skillet over medium heat, add the oil and heat until shimmering but not smoking. Add the broccoli, salt, garlic powder and red pepper flakes and saute until the broccoli is soft and brown around the edges, about 8 minutes. Remove from the heat and add the lemon zest and juice.