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.