Prepare the Tomatoes: Core the tomatoes and cut them into roughly 1-inch pieces. Place them in a large mixing bowl, including any juices collected on the cutting board. This step is crucial as the juices from the tomatoes will enhance the overall flavor of the salad.

Slice the Cucumber: Halve the English cucumber lengthwise and cut it into 1/4-inch slices. If the center is unusually watery, scrape out some of the seeds with a spoon before slicing. This helps maintain the salad's crisp texture and prevents it from becoming too watery.

Add the Onion and Herbs: Add the sliced cucumber, red onion, basil, and parsley to the bowl with the tomatoes. Toss gently so the herbs are distributed without crushing the tomatoes. This ensures that each bite is flavorful and well-balanced.

Make the Vinaigrette: In a small bowl, whisk together the olive oil, red wine vinegar, garlic, Dijon mustard, oregano, salt, and black pepper. The vinaigrette should look lightly thickened and evenly blended. This dressing will bring all the flavors together beautifully.

Dress the Salad: Pour the vinaigrette over the vegetables. Fold everything together gently, lifting from the bottom of the bowl so the tomatoes remain intact. This method helps to coat the vegetables evenly without breaking them apart.

Rest the Salad: Let the salad stand at room temperature for 20 minutes. Stir it once halfway through. The tomatoes will release some juice, creating a light, flavorful dressing. This resting period allows the flavors to meld together.

Taste and Serve: Toss the salad again and taste. Add a small pinch of salt or a splash of vinegar only if needed. Serve with some of the tomato vinaigrette spooned over each portion. This final touch enhances the presentation and flavor of the dish.