Preheat oven to 350°F (175°C). Line an 8x8 baking pan with parchment paper.
In a bowl, whisk almond flour, erythritol, baking powder, cinnamon, and salt.
In a separate bowl, beat eggs, melted butter, and vanilla.
Combine wet and dry mixtures.
Fold in grated carrots and optional nuts.
Pour into pan and spread evenly.
Bake 22–26 minutes or until a toothpick comes out clean.
Let cool completely before frosting.
For the frosting, beat cream cheese and butter until smooth. Add erythritol and vanilla; beat until creamy.
Spread frosting over cooled bars, slice, and enjoy!