Trim off the root end of the romaine, discard any wilted outer leaves. Separate leaves, rinse under cold water, then spin or pat dry. Chop or tear into roughly 1–1.5 inch pieces to measure about 6 cups and place in a large mixing bowl.

Prepare tomato

Core the tomato, then cut into 1/2-inch dice. If using a very juicy tomato, gently drain excess juice before adding to the salad to avoid sogginess.

Prepare onion

Peel the red onion and slice very thinly (about 1–2 mm). If you prefer a milder onion flavor, place the slices in cold water for 5 minutes, then drain and pat dry.

Assemble salad

Add the diced tomato, sliced red onion, and shredded cheddar-jack cheese to the bowl with the chopped romaine. Toss gently to combine and distribute ingredients evenly.

Dressing (simple vinaigrette)

In a small bowl or jar, combine the olive oil, white vinegar, Dijon mustard, honey, salt, and black pepper.

Whisk vigorously (or close the jar and shake) until the dressing is emulsified and slightly thickened, about 20–30 seconds. Taste and adjust seasoning: add a pinch more salt or a little more honey if you prefer a sweeter dressing.

Pour about half the dressing over the salad and toss gently to coat. Serve the remaining dressing on the side for guests who prefer extra.