• Prepare the cauliflower by cutting off the stem and removing the core. If you're steaming in an Instant Pot, you can leave the head intact. If you're steaming in a pot on the stove, cut the florets and stems into pieces that will fit your pot.

For Instant Pot Steaming:

• Place the cauliflower inside the steamer basket with the water. Close the lid and seal the vent. Cook on low pressure for 4 minutes. Manually release the steam and press cancel.

For Stovetop Steaming:

• In a large pasta pot or medium-to-large saucepan, bring 1-2 inches of water to a boil. Place a collapsible metal steamer basket, a stainless steel insert, or a metal strainer/colander into the pot so that it does not touch the surface of the water. Place the chopped cauliflower in the steamer basket or colander. Cover the pot with a lid and steam over medium-high heat until the cauliflower is fork-tender, about 8-10 minutes.

For Both Methods:

• Transfer the steamed cauliflower to a food processor.
• Add 3 tablespoons of the butter and the sour cream. Pulse for 30 seconds or so, until the cauliflower becomes smooth.
• Add the lemon zest, garlic clove, lemon juice, salt, and pepper. Pulse again until the ingredients are well combined. If the mixture is not smooth enough, pulse until you achieve a creamy consistency.
• Transfer the cauliflower to a bowl. Use a spoon to swirl the top of the dish.
• Melt the remaining tablespoon of butter and drizzle it over the dish. Garnish with a lemon slice and additional zest, if desired. Serve immediately.