Mash the Microwave-Roasted Garlic with a fork. Whisk in the lemon juice, then the olive oil. Season with salt and pepper.
Slice the top off the head of garlic and set aside. Put the trimmed head of garlic in a microwave-safe bowl, add 2 tablespoons water to the bowl, drizzle the olive oil over the garlic and sprinkle with a pinch of salt. Put the reserved top back on the garlic and cover the bowl with a plate. Microwave on medium heat until the garlic is very soft, 8 to 9 minutes. Let cool completely, then squeeze the cloves out of the skins into a separate bowl.