Preheat oven to 425°. Zest one of the lemons into a bowl and set aside to save for the sacuce. Cut all of the lemons in half, and squeeze all but one half into another bowl. Save the last half lemon for the sauce.
Cut the top 1 ½ inches off each artichoke, and also cut the stems completely off so that the artichokes will sit flat. Immediately brush the cut surfaces with some of the lemon juice to retard browning.
Pry the leaves apart a little with your fingers. Put an artichoke, stem side down, in the center of a piece of foil. Sprinkle with extra lemon juice, drizzle with melted butter, and season with salt and pepper. Carefully draw the foil up on all sides and completely seal the top by pleating, smoothing, and then twisting the foil. The goal is to encase each artichoke so completely that it’s airtight. Repeat with the remaining artichokes.
Set the artichokes snugly together in a casserole dish, stem side down. Bake for 1 hour 20 minutes. Trust the process, and don’t open the foil before the time has elapsed. Allow them to cool for a few minutes once they’re done, and take care not to get a steam burn when you do unwrap them.
For the sauce, whisk together the sour cream, mayo, Dijon mustard, plus the zest and juice of the remaining half lemon. Add a dash each of salt and pepper. Taste, and adjust seasoning if needed. Serve with the roasted artichokes.