Buckwheat Cake (grain-free, bean-free, sugar-free)

My whole family's concept of cake has changed. My 5 year old insisted that this is cake, although from the look of the ingredients, I'd call it a bread. Nevertheless, we now make it almost every day. I've used organic buckwheat flour from NutsOnline, Arrowhead Mills, and I've also used buckwheat ground at home. We've topped the cake with various nut-butter and also tried putting on chocolate while the cake was still hot and letting it melt, really good!
Will post a pic later

4 cups buckwheat flour or ground buckwheat (about 1 lb.)
1 tsp baking soda
1/2 tsp Frontier garam masala (cardamom, cinnamon, cloves cumin, black pepper, coriander blend)
1/2 tsp ginger root powder
3 & 1/2 cups water
1/4 cup Bragg's Apple Cider Vinegar

1) Preheat oven to 350F. Prepare a 13"x9" pan or one of similar volume. Grease pan with prefered oil. I use a silicone baking sheet nestled inside a stainless steel pan, so I don't have to use oil.
2) Into a large bowl, place buckwheat flour, baking soda, garam masala, and ginger. Mix ingredients together with a fork.
3) Add water and stir until combined, making sure to scrape bottom of bowl with rubber or silicone spatula.
4) Last, add apple cider vinegar and gently fold into mixture with spatula. Be careful not to overmix.
5) Pour batter into prepared pan, place in oven, and bake for 35 minutes.