Put broccoli in a large, microwave safe bowl with a splash of water and cover. Steam broccoli in the microwave for 5-8 minutes or until it's crisp but has lost the "raw" texture. NOTE: I usually use two fresh 12-oz. steam-in-bag bags of broccoli, and cook each one separately in the microwave for 2.5 minutes with great results. When I put all the broccoli together in a single bowl I find it takes longer.
Chill until cold. A couple hours in the fridge should do it, but please see my notes in the post for quicker alternatives.
When broccoli is cold, toss with olive oil, salt, and garlic powder. Add lemon juice and zest and toss again. Adjust seasonings to taste (see notes in post).