Set oven to 325°F (163°C) with a rack in the center. Grease three 8-inch round cake pans. Line each base with a parchment round and lightly dust sides with flour. This prevents sticking and helps layers release cleanly for stacking.

Finely grate fresh carrots using the small holes of a box grater or a microplane. Weigh exactly 360 grams after grating for precise cake moisture. Set aside while you prepare the rest of your mise en place to keep the carrots fresh and bright.

In a large bowl, whisk together sifted flour, baking powder, baking soda, cinnamon, nutmeg, and sea salt. This disperses leaveners and spices evenly throughout the flour to prevent uneven pockets and ensure every slice tastes just right.

In a separate large mixing bowl, combine granulated sugar, brown sugar, and oil. Whisk until glossy and cohesive, about 1 minute, making sure oil suspends the sugars smoothly. Add eggs one at a time, whisking well after each, then add 1 teaspoon vanilla. Mixture should be pale and slightly thickened.

Add the dry ingredients to the wet ingredients in two additions. Fold gently with a spatula until just a few flour streaks remain. Over-mixing at this stage can toughen the layers. Gently fold in the grated carrots until they are evenly distributed and no flour pockets remain.

Divide the batter evenly among the three pans (use a scale for accuracy, about 500 grams per pan). Smooth tops. Bake for 28-33 minutes, rotating pans halfway. Cakes are done when a toothpick inserted in the center comes out with moist, but not wet, crumbs and the edges gently pull from the pan.

Let cakes cool in pans on a rack for 12 minutes. Run a thin knife around the edge. Invert layers onto racks, peel off parchment, and cool completely until no warmth remains (at least 1 hour). This prevents melting your filling or breaking soft cake during stacking.

Beat softened cream cheese and butter together on medium speed until smooth and fluffy, 3-4 minutes. Add remaining 1 teaspoon vanilla and mix briefly. Gradually incorporate sifted powdered sugar. Continue beating until thick, creamy and spreadable with no gritty lumps.

Place one cooled cake layer on a cake plate. Spread a generous coating of frosting (about 3/4 cup) evenly to the edge. Top with the next layer and repeat. Apply the final layer, top with more frosting, and cover sides thinly with a crumb coat. Chill assembled cake for at least 30 minutes to set the crumb before finishing with a smooth, even coating of remaining frosting. Clean your spatula regularly for the sharpest edges.

Return cake to the fridge for another 30 minutes if you want clean, distinct slices. For best presentation, use a hot, sharp serrated knife to cut, wipe clean between slices. Serve straight from the fridge for neater layers or let stand at room temperature for 30 minutes before serving for a softer bite.