Preheat the oven to 350 degrees. Line a large rimmed baking sheet with heavy-duty aluminum foil.
Use a wooden spook to stir together 1/2 cup of the lavender sugar and the 1/4 tsp of salt in a large ovenproof skillet over medium-high heat. Cook, stirring constantly, until the sugar starts to melt, about 2 minutes. Working carefully, continuously stir and scrape the sugar into a pool until most is melted, being careful to avoid splashups.
Immediately transfer the skillet to the oven. Roast (middle rack), stirring every 3 or 4 minutes, until nicely browned and fragrant, but not burned; this should take 7 to 10 minutes.
Remove from the oven; immediately sprinkle over additional garnishing salt, if desired. Stir the pecans well, then spread them out on the foil-lined pan. Use forks to separate any clumps or clusters; don’t touch the nuts, as they will be extremely hot. Let them cool completely, then break up any remaining clumps with your hands before serving or storing.