Prepare the artichokes by removing the stems. Cut off about ¼-inch off the top of the artichoke. Trim the leaves on the whole vegetable. Brush with lemon juice if not using right away.
Add at least one cup of water to the Instant Pot, and the rack. Place the artichokes inside. Drizzle with olive oil, season with salt and pepper, and then top with a pat of butter plus a spoonful of minced garlic.
Cook on high pressure (normal) for 20 minutes (30 minutes for large artichokes) then follow with a quick release.
Serve immediately, or store in an airtight container for up to three days.