1/4 teaspoon finely grated fresh lemon zest, or to taste
2 tablespoons fresh lemon juice
1 tablespoon Dijon mustard
2 teaspoons ground black pepper
1 teaspoon sugar
Scant 1/2 teaspoon salt
3/4 cup olive oil

Whisk together zest, juice, mustard, pepper, sugar, and salt until sugar and salt are dissolved. Add oil in a slow stream, whisking until emulsified.