Sieve whole wheat flour, baking soda, baking powder and salt.
Add oil, sugar and yogurt to a large bowl. Whisk it for a minute until well incorporated.
Add flax egg, lemon zest and vanilla extract. Mix it well.
Add almond flour and gently fold in. Add the sieved wheat flour to the almond mixture.
Fold the flour gently, until no lumps. The batter should be slightly thick.
Grease a 8 inch round baking dish with oil and line it with parchment paper.
Transfer the batter to the baking pan, smooth it out and top it with slivered almonds.