In a bowl, mix milk, eggs, sugar, and oil until combined.
Add lemon juice over the baking ammonia (or baking powder) and stir into the wet mixture.
Add salt, then gradually incorporate flour until a soft, elastic dough forms.
Let dough rest for 30 minutes.
Divide dough into 3 equal parts. Roll each into thin rectangular sheets.
Bake each sheet on baking paper on the back of a tray at 150°C (300°F) for 12–15 minutes. Let cool.
For the cream, whisk together flour, sugar, and lemon zest in a saucepan.
Gradually add milk, whisking constantly to avoid lumps.
Cook on low heat for 20 minutes until thickened. Remove from heat.
Stir in lemon juice and vanilla essence. Let cool slightly.
Add butter in small pieces, whisking gently to incorporate without splitting.
Line the baking tray with cling film. Layer cake: dough sheet, cream, repeat.
Finish with cream on top. Sprinkle with coconut flakes.
Wrap the cake and press with a board and weight (e.g. heavy books).
Refrigerate for at least 12 hours. Serve at room temperature.