Make cake according to directions in 9x13 pan, adding juice of one lemon for part of water. Cool completely then slice into 1 inch cubes.

Beat 1 egg yolk with juice of one lemon and 1/2 small can sweetened condensed milk in medium bowl and set aside.

Beat whipping cream, gradually adding in sugar and lemon extract until soft peaks form. Set aside.

Slice strawberries, removing the stems.

In large trifle dish or bowl, layer 1/2 cake, 1/2 lemon mixture, 1/2 strawberries, and 1/2 whipping cream until completely layered.

Garnish with 4 strawberries cut in half on top.