Plum Cake sounds better than Prune Cake

I made this spicily re-vamped version of a coffee cake recipe for my hubby today. He liked it, and I was pleased because and it's a  healthy dessert and moist enough for the lunchbox.

Yogurt-filled Plum Cake

Grease an 8x8 baking pan with butter

Combine filling ingredients, then set aside:
1 cup strained (Greek-style) yogurt (or plain yogurt mixed with 1/2 tsp xantham/guar gum to thicken)
1 egg
1/4 tsp. salt
1/4 cup raw/natural/brown sugar

Mix dry ingredients:
1 1/2 cups of flour (I used spelt flour)
1/2 cup quick oats
1/2 tsp. salt
1 tsp. baking powder
1/4 tsp. baking soda
1 tsp cinnamon
1/4 tsp. cloves
1/4 tsp. allspice
1/2 tsp. ginger

Cut in:
1/4 cup soft butter
Stir in:
1/2 cup prunes, snipped

Mix wet ingredients:
1 cup buttermilk (or sour milk, or room temperature milk mixed with vinegar/lemon juice)
1 egg, beaten in
1/4 cup raw/natural sugar or honey

Add wet ingredients to dry ingredients. Mix till combined. Pour half the batter into your greased pan. Sprinkle with additional cinnamon. Top evenly with yogurt filling. Top with remaining batter. Sprinkle with walnuts, cinnamon or additional raw sugar crystals if desired. Bake at 350 for 20-25 minutes or till puffy and golden brown.