Combine all ingredients, except for the caramel sauce, into a microwave-safe mug. Mix with a small whisk until batter is smooth.
Cook in microwave for about 1 minute (2 if you are doubling the recipe). Top of cake should be dry. Wait for cake to cool slightly before adding caramel sauce and eating.
Notes
I recommend using regular creamy peanut butter and not natural peanut butter otherwise the texture will not be right.
If you want the cake to have more pumpkin flavor, I recommend using the cinnamon otherwise the cake tastes mostly of peanut butter.
2 tablespoons of an egg is about 1/2 of an extra large egg. If you don't want to use a partial egg double the recipe (like photo in the post) and cook the cake for about 2 minutes, making sure you use a very large mug so it doesn't spill out like mine.
You can add about 1/8 tsp of cinnamon to bring out the pumpkin flavor because it's more of a peanut butter cake than a pumpkin.
The cake itself is not overly sweet, so I recommend using caramel sauce on top.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.