Cut sourdough bread in ¾ inch thick slices.
Combine milk, ½ cup sugar, lemon zest and cardamom seeds in a saucepan. Slowly bring to a boil. Continue to simmer for about 15 minutes, and then turn off heat. Soak the slices of bread in the milk mixture. Do not soak them so thoroughly that they will break apart, but try to absorb as much of the milk mixture as possible.
Set soaked slices of bread aside to cool on a large plate or platter. Some liquid may be lost.
In a deep, heavy pan heat about ½ an inch of olive oil on medium-high heat.
Beat the eggs in a wide, shallow bowl and dip the soaked bread slices in the egg mixture. Fry the bread slices two at a time. Flip after 2-3 minutes and cook until both sides are crisp and golden brown. Let the cooked bread slices rest on paper towels to absorb any excess oil.
Stir together remaining ½ cup sugar and cinnamon. Sprinkle the cinnamon sugar mixture over the bread slices and set any remaining cinnamon sugar mixture aside.
Add remaining cinnamon sugar mixture to a medium saucepan. Add more sugar, if needed, to completely cover the bottom of the saucepan. Add 2 cups of warm water and bring to a boil. Add honey to the mixture and allow the syrup to simmer for about 30 minutes. After simmering, the syrup should no longer be watery.
Remove syrup from heat and let cool for about 15 minutes. Then spoon the syrup over the bread slices. They should be completely soaked in the syrup once you’re done. Allow them to cool completely, and then refrigerate.
Refrigerate torrijas for at least 4 hours, but preferably overnight. Serve within 2-3 days for the best quality.