1. Add 1-inch of water to a medium saucepan and bring to a simmer over low heat. In a medium metal bowl whisk the egg yolks and sugar for about 2 minutes until smooth. Whisk in the lemon juice and zest until combined.
2. Place the mixing bowl on top of saucepan (the bowl should be wide enough to fit on top of the saucepan, but shouldn’t be touching the simmering water). Stir the mixture constantly with a rubber spatula, scraping the bottom and sides of the bowl as you stir, until it begins to thicken, and will coat the back of a spoon. This will take approximately 7 to 10 minutes. Remove from heat.
3. Whisk in the butter, one slice at a time. Wait until each piece almost disappears before adding the next. Spoon into prepared tart shells and refrigerate until you are ready to eat.

Photography

• Camera Nikon D7000 
• Lens Tamaron 90 mm
• Light – Single SB 800 placed right rear, crumpled aluminum foil used to provide front fill light.