Whisk together the egg yolk and dry ingredients into a small glass bowl. In a separate bowl, combine the lemon juice and vinegar, then thoroughly whisk half into the yolk mixture. While briskly whisking, slowly add the oil a few drops at a time, until the liquid seems to thicken and lighten in color. At this point you can slow down the whisking a little and increase the oil flow to a constant, thin stream. After adding half of the oil, whisk in the rest of the vinegar mixture. Continue to whisk until the rest of the oil is fully incorporated. Let set at room temperature for 1 to 2 hours, then refrigerate for up to 1 week.