Crumb topping:
3/4 cup gf flour
3/4 cup brown sugar
1 teaspoon cinnamon
3/4 teaspoon lemon zest
Pinch of salt
1 stick (8 Tablespoons) unsalted butter, softened
3/4 cup walnuts, chopped

Batter:
2 cups gf flour
2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon ground ginger
1/4 teaspoon salt
1 stick (8 Tablespoons) unsalted butter, softened
1/2 cup canola oil
1/2 cup sugar
1/4 cup honey
1 teaspoon lemon zest
1 teaspoon vanilla extract
2 eggs
1/2 cup cream
2 pounds Granny Smith apples - peeled, cored & cut into 1/2-inch dice

Sauce:
1 cup créme fraiche or sour cream
1/4 cup powdered sugar (or more to taste)