Preheat oven to 350 degrees. Spray 8 inch square baking dish with canola oil. Cream together the butter and the brown sugar. Slowly add the eggs and mix. Add the grated apples and walnuts along with the grated nutmeg, ginger, salt and lemon zest. Mix gently. Add 1 tsp baking soda and the flour. Pour into baking dish. Spoon the apple butter into four dollops over the mixture, take knife and work this into the batter. The apple butter adds a delightful moistness. Bake for 38-40 minutes until the toothpick tester comes out clean.