Place the broccoli in a bowl with the olive oil, salt, pepper and lemon zest and toss to coat the broccoli.
Place a in vacuum seal bag and vacuum seal to remove the air (or use the water displacement method).
Heat a water bath to 185F degrees and cook the broccoli for 45 minutes.
Remove the bag from the water and place immediately in an ice bath to stop the cooking.
Remove the broccoli from the bag and serve with fresh lemon juice and additional salt to taste, if necessary.
Notes
If the bag fills with air before the broccoli is cooked, just cut open the bag and reseal it with the vacuum sealer.
If the bag floats, weigh it down with something heavy or drape a wet towel over the top.
For the best results, use a good quality olive oil for the broccoli. You can also substitute butter, if you prefer.
To ensure even cooking, try to arrange the broccoli in a single layer, as much as possible, in the vacuum sealed bag.
The broccoli can be made ahead and stored in the fridge for 5 days or in the freezer for up to 3 months.
To reheat the broccoli, place it in a 150F degree water bath for 5 minutes. You can also reheat it in the microwave, but just use 20 seconds at a time to avoid overcooking.