Preheat the oven to 350 degrees F.

Melt the butter in a 9 inch cast iron skillet or cake pan. Add 1/2 cup brown sugar and 2 teaspoons of the chopped ginger. Heat and stir until the sugar has dissolved. If using a cake pan, place the butter into the cake pan and then put the cake pan in the oven the butter has melted. Stir in the butter and the sugar and then return to the oven for a few minutes until the sugar dissolves.

Carefully add the chopped rhubarb to the pan in a single layer. Set the pan aside.

In a medium sized mixing bowl add the buttermilk, eggs, oil, remaining brown sugar and the rest of the ginger. Whisk until well combined.

Add the flour, salt, baking powder, and baking soda to the mixing bowl. Very lightly stir just the top of the dry ingredients to disperse the baking soda, baking powder, and salt in the flour. Then whisk the dry ingredients into the wet ingredients.

Smooth the cake batter over the rhubarb with a spatula or the back of a spoon, making sure that the cake batter completely and even covers the rhubarb.

Bake at 350 for 30-35 minutes or until the center of the cake springs back when touched and a toothpick inserted in the center comes out clean.

Let the cake cool for 5 minutes on a wire rack before carefully turning the cake out of the pan onto a serving plate.

Serve warm or cold.