Prepare broccoli spears and sliced stems, and steam until crisp-tender (8 minutes.)
In a 1-quart pan, melt butter over medium-low heat. Add garlic and sauté until slightly browned.
In a separate small bowl, blend cornstarch with cold water and then stir into butter/garlic mixture along with salt, sugar, thyme, and lemon zest. Cook and stir over medium heat until thickened and bubbly. Cook and stir 1 minute more.
Remove from heat and stir in lemon juice. Pour over hot drained broccoli.
Use lemon zester or vegetable peeler to remove thin yellow outer peel of a lemon.