Pre-heat the oven to 175°C (350°F) and grease your desired pan (I have used both a 9 x 5" loaf tin and 1 liter bundt).
If using fresh or sliced pineapple, blitz it in a food processor until it is crushed. Remove and set aside.
Using either a food processor or whisk, cream the butter and sugar, and then add in the eggs, one at a time.
Add the crushed pineapple, pineapple juice, oil and yoghurt and continue to whisk until smooth.
Sift the flour, baking soda, baking powder, vanilla sugar, and poppy seeds together and then add to the wet ingredients. Stir until just combined.
Pour into the prepared tin and bake for around 30-40 minutes (depending on which pan you use) in the lower part of the oven.
The cake is ready when an inserted skewer comes out clean. Start checking from about 30 minutes, and if using a bundt tin, you may need to cover the top to prevent it browning too much.
Leave in the tin for a while, then turn out onto a wire rack and cool completely.