Preheat oven to 350 degrees F.
Spray 2 8-inch cake pans with baking spray, cover the bottom to fit with parchment paper and spray again with baking spray. Use 3 pans for thinner layers. Set aside.
Add raisins to a small bowl, top with boiling water and let sit for 10 minutes. Drain well and place on paper towels to dry.
In a medium bowl combine dry ingredients: flour, sugar, baking powder, baking soda, cinnamon, nutmeg and salt. Whisk to combine and aside.
Add wet ingredients to a large bowl: eggs, oil, buttermilk, vinegar, vanilla extract. Using a hand mixer (or stand mixer), whisk on medium speed until fully combined.
Reduce mixer speed to low, and slowly add the dry ingredients mix. Stop from time to time to scrape the sides and bottom of the bowl. Whisk just until fully combined.
Once combined, stir in shredded carrots, chopped walnuts, and raisins.
Divide the batter equally into the prepared pans.