In a small bowl, whisk the red wine vinegar, Dijon mustard, kosher salt, and black pepper until the salt dissolves.
Stir in the finely minced shallot and let sit 5 minutes to lightly macerate.
While whisking constantly, slowly drizzle in the extra-virgin olive oil until the vinaigrette is emulsified and slightly thickened.
Taste and adjust salt or pepper as needed. Use immediately or transfer to a jar, cover, and let stand 10 minutes before dressing salads; shake to re-emulsify before each use.