Oma’s Upside Down Cake

Growing up, most visits to my grandparents’ place involved tea time (which really just meant snacks for us kids). I have fond memories of this cake, as it made regular appearances at tea time every summer. I suppose it may not really be an upside down cake in the usual sense…Oma always kept the cake in the tray it was baked in, and simply sliced and served each piece upside down. I’m not entirely sure whether it’s possible to invert the whole cake onto a plate, but I wouldn’t want to mess with tradition, anyway (Royce confirms – yes, it is possible). As it turns out, this recipe comes together quite easily and is a fantastic way to use up plums when in season (Italian prune plums, to be specific – I used another variety of plums once and was promptly notified of my blunder). As fate would have it the Katsumi farm has both (Italian prune) plum and hazelnut trees, and both are starting to produce quite generously.

When I asked my Oma for the recipe, I found that there were other suggested fruits like peaches or pineapples…but I will always remember this as the plum upside down cake. Years later, we found the original recipe in Oma’s recipe books. A little bookmark indicates a mysterious adjustment to be made, seemingly only when using plums. (As an aside – this only confirms what I’ve always suspected about grandmothers holding back recipe details…innocently or deliberately? The jury is still out…) We tried both versions, and both are good. The real original results in a cake that is (hardly noticeably) a little softer. On principle, this is the version I’ll be using going forward.

Oma’s recipe

The original recipe yields one mystery-sized (non-standard) rectangular baking tray of cake, but we wanted to rework it for the square baking pans that Royce uses with the kids at school. We suggest using the original amounts (below) for two 8″ square pans. With this amount of batter, large plums may peak through to the top slightly, but we think it’s a nice fruit to cake ratio…and it works much better than scaling the recipe by an inconvenient amount that would mess with the volumetric measures.


  • 75g butter (1/3 cup)
  • 100g brown sugar (1/2 cup)
  • 213g flour (1-1/4 cup)
  • 205g sugar (1 cup)
  • 8.6g baking powder (2 tsp)
  • 3.4g salt (1/2 tsp)
  • 80g canola oil (1/3 cup)
  • 192g milk (3/4 cup)
  • 5g vanilla extract (1 tsp)
  • 1 egg
  • 20 plums (in halves)
  • hazelnuts (about 1/2 cup or as many as you like)

Tools Required:

  • small pot (2L)
  • stainless steel bowls
  • whisk/ spatula
  • knife & cutting board
  • 2 – 8″ x 8″ Square baking pan, lined with parchment


  1. Preheat oven at 350°F.
  2. In a small pot, melt butter and brown sugar. Pour mixture evenly into 2 prepared 8″ x 8″ square pans.
  3. While the mixture is still warm, cut plums in half and line the bottom of the square pans with halved plums cut side down. Add nuts in between the plums to fill in the gaps.
  4. In a mixing bowl, sift together flour, sugar, baking powder, and salt.
  5. In a separate mixing bowl, whisk together egg, canola oil, milk and vanilla extract.
  6. Add wet ingredients into dry and mix until combined (careful not to over-mix).
  7. Divide the batter into two (roughly 360g), and pour over the plums. Smooth with a small offset if needed.
  8. Bake at 350°F in a convection oven for roughly 25 minutes, or 50 minutes in a conventional home oven.


  • The original recipe also suggest peaches and almonds or pineapple and pecan halves.

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