I've used this, read it through and see my notes at the end.
carrot-pineapple cake - from Baking Without Fat, by George Mateljan, Health Valley Foods.

2.5 cups whole wheat pastry flour
1.5 teaspoons baking soda
1.5 teaspoons cream of tartar
1.5 teaspoons cinnamon
1/4 teaspoon ground nutmeg
1.25 cups honey
1/3 cup pineapple juice concentrate
2 teaspoons vanilla
2 egg whites, unbeaten
1 8-oz can juice-packed crushed pineapple, drained
2 4-oz jars baby food carrot puree
1 cup raisins
2 egg whites, lightly beaten

Preheat oven to 325. In large bowl, mix flour, baking soda, cream of tartar, cinnamon, and nutmeg. Set aside.

In medium bowl, mix honey, pineapple juice, vanilla, 2 unbeaten egg whites, pineapple, carrot puree.
Stir into flour mixture until just blended. Stir in raisins, then gently stir in the lightly beaten egg whites. Do not overmix.

Spoon batter into 2 9-inch round nonstick baking pans. Bake at 325 for 40-45 minutes or until toothpick in center comes out clean.
Avoid overbrowning. Cool on wire racks 30 minutes, remove from pans.

Notes: I don't see why spelt flour would make too much difference, but perhaps someone else has more wisdom.
I've made this with fresh grated and lightly cooked carrots instead of baby food.
Also used the juice from the crushed pineapple instead of concentrate, I didn't miss the additional sweetness.
I think nuts help, if you don't have allergy issues with them.
I don't use nonstick pans, I grease and flour.

as a sub for wheat flour try barley flour. Similar protein content, but lower gluten. Great for cakes!! Also, you can sub an equal amount of maple syrup for the white sugar.