Make the Tomato Vinaigrette: Place the tomatoes in a dry skillet and lightly char or blister over medium-high heat, just until softened, about 7-8 minutes. If they start popping turn the heat off. (See notes for alternatives.) Place tomatoes, oil, vinegar, maple, shallots, garlic, and basil in a blender and blend until combined (but not overly smooth). Refrigerate.

Make the optional Pickled Shallots and refrigerate.

Make the salad: Combine melon, tomatoes, cucumber, radishes, cucumber, scallions in a large bowl. If making this salad ahead, store this, undressed in the fridge (assembling this right before serving). If serving right away, gentle fold enough of the dressing to lightly coat the salad (you may not need all) along with half of the fresh basil. Taste for salt and acid, adjusting salt and vinegar to taste. Place the salad on a large platter or large shallow bowl. Scatter with the pickled shallots, avocado slices, torn basil and pumpkin seeds. Pour any remaining dressing around the edges of the salad (see photos). Serve immediately- you really want this salad served cold.