Finely grind pecans in a food processor (or use equivalent in pecan meal). Add flour and salt, then pulse to combine.
In a bowl, stir together butter and granulated sugar, then stir in egg yolk. Add flour-pecan mixture and mix with fingers until mixture has the texture of fine crumbs and holds together when pressed between two fingers.
Put parchment on the bottom of an 8 1/4-by-11-inch tart pan with a removable bottom. Press crumbs evenly into bottom and up sides of the pan
Freeze crust for 15 minutes. Bake in 375 F oven until set and golden brown, about 25 minutes. Transfer pan to a wire rack and cool for 15 minutes.
Prepare Filling:
While crust is baking, whisk together brown sugar, cornstarch, and salt in a saucepan. Whisk in egg yolks, then milk. Bring to a boil, then reduce heat and simmer 1 minute. Remove from heat and whisk in butter. Pour filling into crust and let cool 15 minutes. Place wax paper directly onto surface of filling and refrigerate until set, at least 4 hours and up to 2 days.
Before serving, remove wax paper and re-smooth pudding top (it does not set too firmly to do this). Decorate top with extra pecans if desired.
I am not a health professional and nutrition data is calculated programatically. Accuracy may vary with product selection, calculator accuracy, etc. Consult a professional for the best information.