For the roasted garlic

1. Preheat the oven to 400°F.
2. Cut the top 1/4 inch off of the bulb of garlic, exposing the cloves.
3. Put the bulb of garlic on a sheet of aluminum foil that is large enough to wrap the entire bulb.
4. Drizzle the bulb of garlic with the oil, then sprinkle with the salt and pepper.
5. Wrap each bulb tightly in the foil. Put the foil packets on a rimmed baking sheet and bake for 45 minutes, or until the garlic is fragrant and the cloves are tender and caramelized.
6. Once the garlic has cooled, squeeze the cloves out of the bulb and mash them into a paste. 

For the mayo

1. Starting with the lemon juice and ending with the avocado oil, put the ingredients, one at a time and in the order listed, in a wide-mouth pint-sized mason jar. Let the ingredients rest for 20 seconds or so.
2. Insert an immersion blender into the jar, placing it all the way at the bottom. Turn it on high speed and leave it at the bottom of the jar for about 20 seconds. The mayonnaise will immediately begin to set up and fill the jar.
3. When the mayonnaise is almost all the way set, slowly lift the immersion blender toward the top of the jar without taking the blades out of the mayonnaise. Then slowly push it back toward the bottom of the jar. Repeat this up-and-down motion a couple of times until the ingredients are well incorporated. 
4. Gently mix in the garlic paste.