In a skillet, prepare onion and leek the Enlitened way, as follows: heat olive oil with cooking spray in a large nonstick skillet over medium heat for a few seconds. Add the leeks and onions, stir and lower heat. Cook until leeks and onions start to brown, stirring occasionally. Cook another few minutes, scraping the bottom of the pan so that nothing sticks.
Slice zucchini into chunks, add to onions, and sprinkle salt on top.
Add this to the skillet and leave on low heat for 1 1/2 hours, stirring every so often. The zucchini will soften and then turn brown from the onions.