Add the soy milk and the lemon juice to a large mixing bowl and set aside for 5 minutes to thicken and curdle. (This is your vegan buttermilk.)
Preheat the oven to 350°F/176°C and grab a nonstick muffin tin. (Or grease your tin or liners if needed.)
Once curdled, add the remaining wet ingredients to your bowl and mix well. Then add the dry ingredients to the same bowl and stir until combined WITHOUT over-mixing. (If using an optional fill-in, fold those in as well.)
Divide the cupcake batter among your 12 muffin cups and bake until a toothpick inserted in the center of a cupcake comes out clean, approx 18 minutes. Remove from the oven and let rest for 10 minutes before transferring to a cooling rack.
For the frosting
Add all the frosting ingredients to your blender and process until smooth. Start with 5 tablespoons of the maple syrup, then taste, and add more until desired sweetness is reached. Don't go overboard or the frosting will be too soft.
Once the cupcakes are completely cooled, frost your cupcakes with a piping bag, and enjoy.
Notes
Weigh your flour for the most accurate results. I highly recommend that you do not rely on cup measurements when baking. If you don’t have a kitchen scale, you may spoon the flour into your measuring cup and use a knife to scrape off the excess, with similar results. Do not scoop from the bag!
Use a box grater or food processor to shred your carrots, but either way, freshly grated is best as store-bought shredded carrots may be dry.
Don't overmix the cupcake batter. Stir until there are no floury bits, but don't worry about working through every lump. Over-mixing can result in a gummy or dense texture.
Use fresh and active baking powder. Baking powder that is open in your pantry for 6+ months can start to lose its effectiveness.
Since these cupcakes have no added fat, make sure to use a non-stick muffin tin OR grease your pan or cupcake liners to prevent sticking.
If you do not have a powerful blender, soak your cashews in hot water for 30 minutes before blending your frosting. This will help them swell and soften, making them easier to blend into a smooth frosting.
Drain and pat your tofu dry to remove some excess liquid and prevent your frosting from getting too thin.
If the frosting gets warm as you’re blending (this can happen in strong blenders), transfer it to a bowl and place it in the freezer for 30 minutes before piping the frosting onto your cupcakes.
Let your cupcakes cool in the muffin pan for at least 10 minutes before handling them. Then transfer them to a cooling rack to completely cool BEFORE frosting them.