Red-leaf Lettuce and Celery Salad

• 1 cup water
• 1/2 cup chopped onion
• 2 tablespoons Sherry vinegar
• 1 teaspoon caraway seeds, toasted
• 1 teaspoon sugar
• 3/4 teaspoon dry mustard
• 1/3 cup olive oil
• 1 head of red-leaf lettuce, torn into bite-size pieces
• 3 large (outer) celery ribs, very thinly sliced on a long diagonal (about 3 cups)
• 1 cup tender inner celery leaves, coarsely chopped

Simmer water and onion in a small saucepan, uncovered, until onion is softened and most of water is evaporated, 10 to 15 minutes. Purée in a blender with vinegar, caraway seeds, sugar, mustard, and 1/2 teaspoon salt. With motor running, add oil in a slow stream and blend until dressing is emulsified.
Combine lettuce, celery, and celery leaves in a large bowl and toss with just enough dressing to coat.
Adapted from epicurious.com