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1
Assemble the ingredients.
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2
Bring the butter to room temperature.
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3
Put the sugar and lemon zest in a bowl and rub together with your hands to mix.
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4
Put the egg, lemon juice, and sugar in a heatproof bowl and mix.
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5
Put on a double boiler and continue mixing with a whisk.
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6
When it becomes just a bit softer than custard (about 83C), remove from the heat and continue mixing.
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7
Keep mixing until it reaches about 60C (140F), then add the butter one tablespoon at a time.
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8
Mix with an electric mixer as you go.
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9
Keep mixing for about 5 more minutes, then you're done.
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10
Transfer to an airtight container, wrap with plastic wrap, and let cool.
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11
When cooled, store in the refrigerator overnight.
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12
If using for a macaron filling, add the almond flour the next day, then fill the macarons.
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13
Use it to fill lemon-flavored macarons!
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14
Here's a recipe for Lemon Macarons..
