Prep the pan and oven. Preheat the oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper, leaving overhang for easy lifting. Lightly grease the parchment.

Mix the dry ingredients. In a large bowl, whisk the flour, granulated sugar, brown sugar, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger until no lumps remain.

Whisk the wet ingredients. In a separate bowl or large measuring cup, whisk the eggs, oil, applesauce (or yogurt), and vanilla until smooth and combined.

Combine batter. Pour the wet mixture into the dry ingredients. Stir gently with a spatula until just combined and no dry streaks remain. Do not overmix.

Fold in carrots and add-ins. Fold in the grated carrots and any optional mix-ins like nuts or raisins. The batter will be thick and speckled with carrots.

Fill the pan. Scrape the batter into the prepared pan and spread it into an even layer using an offset spatula or the back of a spoon.

Bake. Bake for 25–32 minutes, or until the center springs back lightly to the touch and a toothpick inserted near the center comes out with a few moist crumbs.

Cool completely. Place the pan on a wire rack and let the bars cool fully in the pan. This keeps them moist and makes frosting easier.

Make the frosting. In a mixing bowl, beat the cream cheese and butter together on medium speed until smooth and fluffy, about 2–3 minutes. Add 2 1/2 cups powdered sugar, vanilla, salt, and orange zest if using. Beat until creamy. Add more powdered sugar to reach your desired thickness.

Frost the bars. Spread the frosting over the cooled bars in an even, thick layer. For a cleaner look, chill 15 minutes before slicing.

Slice and serve. Use the parchment overhang to lift the bars from the pan. Cut into 20–24 squares. Garnish with a sprinkle of cinnamon or chopped nuts if you like.