In a bowl, combine peaches, sugar, vanilla seeds, lemon zest, and lemon juice (make sure it equals at least 3 tablespoons). Toss to coat. Cover and refrigerate at least 2 hours or overnight.When you are ready to proceed, prepare canner and wash/sterilize 2 half-pint (or equivalent) mason jars. Keep jars in hot (not boiling) water until ready to use.Pour peach mixture into a large, heavy saucepan or skillet and place over high heat. Cook, stirring regularly, until the peaches soften, the liquid reduces, and the whole mixture becomes quite thick and spreadable, about 10 to 12 minutes.Ladle hot jam into prepared jars, leaving 1/4-inch of head space. Wipe jar rims and threads. Screw on lids and rings. Process in a boiling water bath for 10 minutes. Remove from water and let cool completely, 12 to 24 hours. Check seals. Any unsealed jars should be refrigerated and used within 3 weeks.