Preheat oven to 350°F (175°C).

Grease and flour a 13 x 9-inch baking pan.

Pour boiling water over dry oatmeal in a bowl.

Add baking soda to the oatmeal mixture.

Let the oatmeal mixture sit for 10 minutes to soften.

In a separate bowl, cream together butter, brown sugar, and white sugar.

Add eggs to the butter and sugar mixture and mix well.

Add the oatmeal mixture to the butter, sugar, and egg mixture.

Gradually add flour, nutmeg, cinnamon, and salt to the batter.

Mix all ingredients thoroughly until well combined.

Pour the batter into the prepared baking pan.

Bake in the preheated oven for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.

Let the cake cool in the pan before serving.

Optionally, dust with powdered sugar or add icing.