Preheat oven to 350F and grease a 9x13 pan.
Melt the white chocolate and butter in a microwave with 30 seconds intervals. Stir until smooth. Let it cool.
In a large bowl beat eggs and sugar until pale color. Beat in the white chocolate mixture and vanilla.
Combine flour and salt into the egg mixture and beat until combined.
Spread into a greased 9x13 pan.