Preheat the oven to 180°C/160℃ fan/350°F/gas mark 4. Grease a 2lb loaf tin and line it with greaseproof paper.
If using fresh passion fruits, briefly pulse the flesh in a food processor or blender to separate the juice from the seeds, then press it through a fine mesh sieve to extract as much juice as possible. Weigh out 120g of seedless pulp; if you are slightly short you can top it up with non-dairy milk to 120g.
In a large bowl whisk together the seedless passion fruit pulp, yogurt, sugar, oil, melted butter and vanilla.
120 g (½ cup) seedless passion fruit puree* (see notes), 180 g (¾ cup) vegan Greek style yogurt, 200 g (1 cup) caster or granulated sugar, 55 g (¼ cup) neutral oil (olive/sunflower/canola/avocado), 100 g (7 Tablespoons) vegan block butter, 1 Tablespoon vanilla bean paste or extract
Whisk in the cornflour, baking powder, bicarbonate of soda and salt, followed by the plain flour. Mix until no dry lumps remain but be careful not to overbeat the batter.
20 g (2 packed Tablespoons) cornflour (cornstarch), 2 teaspoons baking powder, ¼ teaspoon bicarbonate of soda (baking soda), ¼ teaspoon salt, 270 g (2 ¼ cups) plain (all-purpose) flour
Scrape the mixture into the prepared loaf tin and bake for about 60 minutes until a skewer inserted into the centre comes out clean.
Leave the cake to cool in the tin for 10 minutes then carefully turn it out onto a wire rack and leave to cool completely.
Once the cake has cooled make the glaze; sift the icing sugar into a bowl and stir in the passion fruit pulp and melted butter to form a thick but spoonable glaze. Add more icing sugar if it is too runny or a squeeze of lime or lemon juice if it is too thick.
pulp from 1 passion fruit (including seeds), 15 g (1 Tablespoon) vegan block butter, 115 g (1 cup) icing (powdered) sugar, a squeeze of lime/lemon juice as needed
Spoon the glaze over the cake and serve. Store in an airtight container at room temperature.