Preheat oven to 375°F. Line a baking sheet with parchment paper and set aside.
Using a serrated knife, cut the bagels into large chunks. Toss with olive oil and spread out in an even layer onto the prepared baking sheet. Bake until golden brown and toasted, about 8 to 10 minutes. Remove from the oven and allow to cool completely.
In a large bowl, toss together the tomatoes, cucumber, red onion, radish, capers, avocado, and dill. Season with a pinch of salt and pepper.
For the dressing, in a food processor combine the cream cheese, buttermilk, lemon juice, chives, garlic and a pinch of salt and pepper. Slowly drizzle in the olive oil and blend until smooth. If you want it slightly thinner, drizzle in more buttermilk as needed.
Right before serving the salad, toss the toasted bagels into the tomato mixture along with your desired amount of dressing and then top with the smoked salmon, if using. Garnish with more fresh dill and serve immediately. Enjoy!