Add the bagel seasoning to a large rimmed dish, like a 9x13' casserole dish.
Unwrap both pieces of dough, but leave them in the log shape from the can. Do NOT unroll them.
Spray a large bundt pan liberally with non stick cooking spray. Add one of the dough logs to the bagel seasoning, and keeping the ends clear roll it in the seasoning to evenly coat it.
Transfer the dough to the prepared bundt pan to cover one half of the bottom. Repeat with the seasoning coating for the remaining log of dough, and place it in the other half of the bundt pan. Pinch the edges together tightly to seal the two pieces into one single ring of dough.
Bake the dough at 350 degrees for 35 minutes, or until the bread's cooked through and golden brown on top. Remove the bread from the oven, and let it rest cooling for 10 full minutes.
Carefully release the bread from the pan onto a cooling rack, and let it continue to cool completely- roughly another 30 minutes or so.
Using a serrated bread knife, carefully cut the loaf of bread in half horizontally. Place both halves, inside up, on a large cutting board.
Leaving a half inch crust around each half, tear bread from the centers to create a trough that goes all the way around each piece. Discard the torn bread, or save it for another use.
Melt the butter in a medium sized skillet (about 10 inches) over medium heat. Once the butter's melted and coated the skillet, pour the beaten eggs into the pan.
Reduce the heat if needed, and let the eggs cook until firm but soft- stirring as needed to bring uncooked egg to the center like a frittata.
Remove the skillet from heat, top the eggs with the shredded cheddar, and cover the skillet allowing it to melt.
Spread the softened cream cheese evenly out into the troughs of the bread. Press the spinach leaves gently into/over top of the bottom loaf.
Carefully release the egg frittata from the skillet and slide it out on top of the spinach covered bottom loaf.
Top the bundt-wich with the top loaf of bread, and use the serrated bread knife to cut it into sandwich sized wedges for serving.