Place olive oil in jar (or container with a similarly-sized base). Add the egg and lemon juice only.
Place immersion blender into the jar with the blades directly on top of the yolk. Blend on high, holding the blender to the bottom of the jar until you see it emulsify, or look “fluffy” with the separate oil on top. Probably, about 20 seconds. Slowly lift the blender to to top of the oil, incorporating oil a little at a time. Once at the top of the oil, you can move the blender around to get what’s left of the oil. At this point you can move the blender up and down in the jar and you should see it’s nice and thick.
Turn of blender and add salt and garlic powder. Position blender over spices and blend on high, moving the blender up and down the mayo to fully incorporate it.
Ingredients emulsify best if they are at room temperature.