Prepare your ingredients: Drain and rinse the white beans well. If using a fresh garlic clove, peel it and roughly chop it. Juice the lemon and measure out the remaining ingredients.
Blend the dressing: Add the white beans, lemon juice, Dijon mustard, nutritional yeast, garlic (or garlic powder), capers (if using), and 3 tablespoons of water to a blender or food processor. Season with a pinch of salt and freshly ground black pepper.
Blend until smooth and creamy: Blend on high for 30–60 seconds, or until completely smooth. Scrape down the sides if needed. Add an extra tablespoon of water if the dressing is too thick.
Taste and adjust: Taste the dressing and adjust to your liking. Add more lemon juice for brightness, more mustard for zing, or more capers for salty brininess. Season with additional salt and pepper if needed.
Serve or store: Use immediately over romaine salad, as a dip for veggies, or in wraps and bowls. Store leftovers in an airtight jar in the refrigerator for up to 3 days.