Get out a 9 x 13 baking dish and spray it well with cooking spray. Add the diced up bagels to it in an even layer. Then sprinkle the chopped smoked salmon, scallions, capers and fresh tomato evenly over the bagels. In another bowl, whisk the eggs, milk, cream cheese, salt, pepper and garlic powder together thoroughly. Pour it evenly over the casserole, then press everything down lightly to make sure the casserole is even and submerged. Cover it and refrigerate it overnight. In the morning, pre-heat the oven to 350. Bake the casserole for 45-50 minutes, until it is set and the bagels start to crisp around the edges. Let it cool and set for just a couple of minutes, then cut it and serve immediately. Enjoy!