From Kate Nelson, Piecurious Catering and Pie Company, Dallas:

This pie is reserved for the true blue Texas grapefruit fan, and not for the faint of citrus. The texture is that of a key lime pie with the appearance of a lemon chess pie. Kate Nelson developed this recipe for the Texas Grapefruit Dinner, hosted by chef Graham Dodds. “He provided me with the best batch of Rio Grande Valley grapefruit that I’d ever seen,” says Nelson. “My goal is to create the freshest farm-totable pie that I can. I always have wonderful luck at Dallas Farmers Market.”

Use the “spoon test” to determine if you have cooked the filling long enough. “This test was passed down to me,” says Nelson, “by the long line of matriarchal bakers in my family and has stood the test of time. Before removing the filling mixture from the heat, take a teaspoon and dip out a bit of the filling. Let the spoon rest for about 30 seconds. Spin the spoon upside down and hold it that way. If the filling stays and does not drip or droop down, the filling is finished and is sure to set up properly. If it drips or droops down, boil the filling five additional minutes and repeat the test. This trick is extremely useful for all pie fillings that require boiling.”