Mix the flour, semolina, baking powder and sugar. Dissolve the baking soda in yoghurt and while stirring constantly with a whisk, add the dry ingredients. Beat well.
Grate the pumpkin and mix it with the walnuts, vanilla and cinnamon. Grease an oven dish and put 1/2 of the dough in it, add the filling on top and then the rest of the dough. Put the cake to bake in moderate oven until ready.
Optionally sprinkle the semolina pumpkin cake with powdered sugar.