Separate the egg yolks from the egg whites. In a heatproof bowl off the heat, begin whisking together your egg yolks, 1/4 cup sugar, vanilla bean seeds, and lemon zest with a whisk or hand mixer until slightly paler in color and thickened. Place the heatproof bowl over a simmering pot of water and continue to whisk and cook until it reaches around 165F and it becomes thicker and paler. Take it off the heat and whisk for another minute. Set aside to allow it to cool.
In a stand mixer, whisk the cream of tartar and egg whites on high speed. When tracks begin to form, gradually add in the 1/4 cup of sugar. Continue to whisk on high speed until shiny, stiff peaks form.
Gently fold the meringue into the egg yolk mixture.