Drizzle approximately 2 tablespoons of olive oil in a stock pot or dutch oven. Turn heat to medium high.
Add onions, smashed garlic, and chopped tomatoes. Season with about 2 teaspoons of kosher salt, cayenne (use less if nervous, but 1 tsp for me wasn't too hot), and black pepper, to taste. Cook until tomatoes start to release juices and begin to boil. Then cover and reduce heat. Simmer for about 15 minutes, or until onions and garlic are translucent and tomatoes are very mushy.
Add bread pieces and stir, letting them soak up the tomato juices.
Ladle about 1/2 of the tomato mixture to the blender. Place the lid on the blender and using a towel (preferably one you don't care too much about in the event of some splatter), cover the lid. Blend starting on low and gradually increase speed to high. At this point you can remove the vent for the blender without much risk of spatter. Slowly drizzle in 1/4 of olive oil. Mixture should emulsify and change color to a bright orange-red. Pour emulsified soup out into a separate pan or bowl.
Repeat the blender/olive oil emulsion step for the remaining soup.
Finally, pour all the soup back together. Taste and add 1-2 additional teaspoons of salt as needed as well as more pepper, if desired.
Garnish with diced fresh tomato, chives, and additional black pepper as desired.