Preheat the oven to 170 ° C. Grease a baking pan of approx. 25 x 25 cm with butter and line the base with baking paper.
Beat the eggs with the sugar to a thick cream. Thoroughly mix in the butter, olive oil, milk and vanilla pulp. Sift the flour, baking powder and salt into the bowl, add the citrus peel and mix everything thoroughly with a wooden spoon. Then let the dough rest for 10 minutes - this allows the flour to swell a little.
Then fold about half of the berries into the dough, place the dough in the mold and smooth it out. Bake the cake on the middle rack for about 15 minutes.
Take out and sprinkle with the rest of the berries, then press them carefully into the batter. Put in the oven for another 30-40 minutes, until it feels firm and is golden brown on top.
Let cool on a wire rack in the tin for 10 minutes. Remove from the edge with a knife and lift out in portions.