In a large saute pan, heat the olive oil over medium-high heat. Add the onions, season with salt and cook 2 to 3 minutes, stirring to avoid any burning. Add the zucchini, herbes de Provence, and salt, and pepper, to taste and cook an additional 5 minutes, using a wooden spoon or spatula to keep the vegetables from overbrowning. Reduce the heat to low, add a little more oil if needed and let cook for 20 to 30 minutes, stirring occasionally. Once it's done, you can turn off the heat and let it sit there on the stove top or just let it cook some more over very low heat; the dish is very flexible.