1. Preheat oven to 400℉.
2. Spray a 9×13-inch glass baking dish with cooking spray and set aside.
3. Using a large knife, cut each artichoke in half and use a spoon to scrape out the fuzzy choke. 
4. Brush all sides of the artichokes with lemon juice and place cut-side down in the baking dish. 
5. Roast artichokes for 15 minutes. Remove baking dish from oven and flip the artichokes over so the cut side is up. 
6. Sprinkle artichokes with garlic and drizzle with oil. Sprinkle with salt and pepper. 
7. Place a lemon slice and sprig of thyme on top of each artichoke half (sprinkle with dried thyme if not using fresh). Lightly spray artichokes with cooking spray. 
8. Cover the baking dish tightly with foil and return the dish to the oven. 
9. Bake for 35-45 minutes or until you can easily insert a paring knife into the heart (or the bottom of the stem) and the lower leaves are easily pulled from the artichoke. 
10. Remove from the oven and serve hot or at room temperature drizzled with vinaigrette. 
11. Leftover artichokes may be stored in an airtight container in the refrigerator for up to 4 days. 

To make the vinaigrette:

1. Combine oil, vinegar, lemon juice, shallot, mustard, and thyme in a small bowl and whisk to combine. Season with salt and pepper to taste. 
2. Leftover vinaigrette may be stored in an airtight container in the refrigerator for up to 1 week.