Preheat the oven to 350 degrees. Spray a 12-cup muffin tin with non-stick cooking spray and set aside. \nIn a large bowl, sift together the flour, baking powder, baking soda, salt and India spice until combined.\nIn a separate bowl, whisk together the melted butter and sugar until homogenous. Stir in the sour cream, vanilla and eggs until incorporated and smooth. Pour the wet ingredients into the dry ingredients and mix until completely incorporated and no lumps remain, being careful not to over mix.\nNext, make the crumble topping: Combine all of the crumble ingredients except for the nectarines. Mix together until the butter is completely incorporated and the topping resembles the texture of wet sand (it may help to use your hands!). \nEvenly divide the batter among your muffin tins (it should be thick). Top each with some of your nectarines, followed by a heaping spoonful of crumble topping. Bake for 15-20 minutes, rotating once halfway through, or until a toothpick into the center comes out clean. Let cool in the tins before removing.