Trimming the artichoke: Cut the stem leaving about ½ inch. Cut off the top ¼-1/3. Remove tough leaves from bottom layer and use kitchen shears to trim the tips of any remaining leaves.
Slice the artichokes in half vertically. Use a spoon to remove the fuzzy part in the middle of the artichoke. Rub all of the cut surfaces with a lemon half to prevent browning. Place the artichoke halves on a baking sheet cut-side-up. Brush with the olive oil.
In a small bowl combine chopped garlic, herbs, salt and pepper to taste.
Stuff the artichoke cavities with the garlic herb mixture and carefully flip over. Brush the artichokes with oil, and season with salt and pepper if desired.
Bake uncovered for 15 minutes. Tent the artichokes with a piece of aluminum foil, and bake until the artichokes are tender and the leaves pull off easily, about 25 more minutes.
Drizzle the artichokes with fresh squeezed lemon juice. Remove the herbs and garlic and place in a mixing bowl with yogurt and mayonnaise. Stir to combine.
Serve artichoke halves with dipping sauce on the side.