In a liquid measuring cup, add the almond flour, baking soda, and salt. Whisk until uniform.
Add the black sesame paste, maple syrup, avocado oil, vanilla extract, and egg. Whisk the batter until smooth.
If you want the mug cake to look pretty, pour the batter into a microwave-safe mug (6- to 8-ounce size is optimal). However, you can totally microwave the cake in the glass liquid measuring cup if you want to cut down on dishes to wash.
Place the mug in the center of your microwave (it will rise more evenly in that spot), and cook on high power for 1-2 minutes. I have a 900 watt microwave and my mug cakes are done in 90 seconds. Adjust the cooking time depending on the strength of your microwave—decrease the time if you have a higher wattage microwave and increase it if you have a less powerful microwave.
The black sesame mug cake is finished cooking when it puffs up and a toothpick inserted into the center comes out clean. Don’t worry if your cake looks lopsided or collapses—it will still taste great!
Let the cake cool for a few minutes and top with candied eyeballs, if desired.