Carrot Cake Sheet Cake

Ingredients:2 cups all-purpose flour
2 tsp baking powder
1 tsp baking soda
1 tsp ground cinnamon
1/2 tsp salt
1 1/2 cups granulated sugar
3 large eggs
1 cup vegetable oil
2 cups grated carrots
1 cup chopped pecans or walnuts (optional)
For the frosting:
8 oz cream cheese, softened
1/2 cup unsalted butter, softened
4 cups confectioners’ sugar
2 tsp vanilla extract