Heat oven to 325° F. Combine the butter, sugar, and salt in a mixer and beat until light and fluffy. Blend in the lemon zest, loose tea, and flour until smooth. Press into an 8-inch square cake pan. Bake 30 minutes or just until the shortbread begins to turn golden. Cut into 9 squares, then cut each square into 2 triangles. Cool completely on a wire rack. Remove the shortbread cookies from the pan.