Preheat the oven to 350 degrees Fahrenheit or 180 Celsius.
Prepare you cake pan. I used an 8 inch pan in the video. You can also you a springform pan or any other sizes of cake pans (this will change the baking time). Rub butter on the sides of the pan and a bit on the bottom. Place a circular piece of parchment paper on the bottom. Set aside.
Combine the dry ingredients in a medium mixing bowl: flour, turmeric, cinnamon, ginger (spice), salt, baking powder and soda. Mix until combined. Set aside.
In a stand mixer or using a hand mixer, combine the wet ingredients. Beat the softened butter, brown sugar and molasses until the mixture is light, airy, a bit fluffy and far more pale than when the ingredients began being combined. (about 3-4 minutes). Be sure to scrape down the sides of the bowl from Time to time. Add the freshly grated ginger. Beat to combine.
Add eggs to the wet mixture and mix until light and fluffy. It will almost looking like a light caramel frosting. This will take about 5 minutes. Add the chopped crystalized ginger.
Add the buttermilk and vegetable/canola/coconut oil gradually, alternating with the dry ingredients. Add a 1/3 of the buttermilk mixture, then a 1/3 of the dry ingredients. Mix on a low speed. Then add the next third. Mix. Then add the next third. Mix until all ingredients are combined.
Place the batter into the prepared cake pan. Sprinkle on the Demerara sugar. Be generous as this adds a lovely crunch to each bite of the cake.
Bake for 35-40 minutes (for an 8" cake pan).
When you check the cake after 35 minutes. Likely, the middle will see a bit uncooked. This is actually okay. The cake should be a near dark brown, but you do want the softness in the middle. Let the cake cool for 30 minutes at least as this will give the middle time to settle. The middle (as you see in the pic) will sink. That is okay as well as you want a bit of different texture from the outer crisp edge and top to the chewy, soft middle.