Preheat the oven to 325F (165C). Grease and line the bottom and sides of a 8 inch (20 cm) pan with parchment paper.
Separate whites from yolks.
In a medium bowl mix yolks with 1/3 cup (70g) sugar and vanilla extract, until creamy and pale yellow colored. Gradually mix in oil and then add sparkling water. Sift the flour, cocoa powder, instant coffee and baking powder over the yolk mixture and gently fold them in.
In a large bowl mix egg whites with salt until foamy. Gradually add remaining 1/3 cup (70g) sugar.
Continue mixing until stiff peaks form.
Gently fold a spoon of whipped whites into the yolk mixture and then gently fold the yolk mixture into the whipped whites.
Pour the batter into the prepared pan.
Bake for 40-45 minutes, until a toothpick inserted into the center comes out clean.
Let it cool for about 10-15 minutes. Remove from the pan and cool completely on a rack.