Preheat oven to 325°F (163°C). Line an 8x8 inch baking pan with parchment paper.
In a microwave-safe bowl, melt white chocolate and butter in 15-30 second increments, stirring in between until smooth.
In a mixing bowl, whisk together eggs and sugar until light and fluffy (about 3 minutes).
Combine flour and salt, then gradually fold into the wet ingredients until just combined. Avoid overmixing.
Pour the batter into the prepared baking pan and bake for 29-33 minutes, or until the edges are lightly golden. Let cool completely before slicing.