Place the sliced red onion in a jar or small bowl. In a separate container whisk together white wine vinegar, water, sugar and salt until dissolved. Pour the pickling liquid over the onions, pressing them down so they are submerged. Let sit at least 15 minutes at room temperature (up to 2 hours for more flavor). Drain before adding to salad.

Garlic breadcrumbs

Toast breadcrumbs

Preheat oven to 375°F (190°C). Toss bread cubes with 2 tablespoons olive oil, minced garlic, 1 tsp salt and 1 tsp black pepper on a baking sheet. Spread in a single layer and bake 10–12 minutes, tossing once, until golden and crisp. Cool on a rack.

Fresh tomato vinaigrette

Blend vinaigrette

Place the chopped seeded tomato, 3 tablespoons olive oil, red wine vinegar, Dijon, honey, minced garlic, 1 tsp salt and 1 tsp pepper in a blender or food processor. Pulse until mostly smooth but still slightly textured (about 6–8 pulses). Taste and adjust seasoning. If too thick, thin with 1–2 teaspoons water.

Salad assembly

Combine and toss

In a large bowl combine the tomatoes (from the salad base), cucumber slices, chopped romaine, arugula, torn basil and crumbled feta. Add the avocado cubes gently to avoid mashing. Add the drained pickled onions and about two-thirds of the garlic breadcrumbs.

Dress the salad

Pour the fresh tomato vinaigrette over the salad—start with about 3 tablespoons, then gently toss to coat. Taste and add more vinaigrette as desired (up to the full amount). Let the salad sit 5 minutes so flavors meld and bread absorbs some dressing.

Finish and serve

Just before serving, sprinkle remaining garlic breadcrumbs over the top for crunch. Adjust salt and pepper to taste and garnish with a few extra torn basil leaves. Serve immediately.