For filling, in a small mixing bowl stir together the ricotta cheese, cream cheese, radish, chives, desired snipped fresh or dried herb, and onion salt. Mix well. Set aside.
Slice a thin layer off the top of each tomato. Using a small spoon, carefully scoop out and discard pulp. Invert tomatoes onto paper towels to drain. If using squash, cut in half lengthwise for zucchini or horizontally for pattypan; scoop out pulp and invert as for the cherry tomatoes.
Stuff the tomatoes and/or squash with filling. Serve immediately or chill until serving time. If desired, garnish with additional desired fresh herb. Makes 10 to 12 servings.
Make Ahead Tip:
Prepare filling and stuff vegetables as directed. Arrange stuffed vegetables on a plate; cover and chill up 2 hours. Garnish just before serving.