In the bowl of a stand mixer fitted with the paddle attachment, beat 1 cup (125g) flour, 1/4 cup (50g) granulated sugar, yeast, 1 teaspoon (3g) salt, and 1/4 teaspoon cinnamon at medium-low speed until well combined.
In a medium saucepan, heat milk and softened butter over medium heat until an instant-read thermometer registers 120°F (49°C) to 130°F (54°C). Add milk mixture to flour mixture; beat at medium speed for 2 minutes. Add eggs, lemon zest, and 1 teaspoon (4 grams) vanilla; beat at medium-high speed for 2 minutes. With mixer on low speed, gradually add 2¼ cups (281 grams) flour, beating just until combined and stopping to scrape sides of bowl.
Switch to the dough hook attachment. Beat at medium speed until a soft, tacky dough forms, 6 to 8 minutes, stopping to scrape sides of bowl and dough hook; add up to 1/4 cup (31g) flour, 1 tablespoon (8g) at a time, if necessary. (Dough should pass the windowpane test [see Note] but may still stick slightly to sides of bowl.)
Spray a large bowl with cooking spray. Place dough in bowl, turning to grease top. Cover and let rise in a warm, draft-free place (75°F/24°C) until doubled in size, 40 minutes to 1 hour.
Line 2 (8½x4½-inch) loaf pans with parchment paper, letting excess extend over sides of pan.
In a small bowl, stir together ginger, remaining 1/4 cup (50g) granulated sugar, remaining 1 1/2 teaspoons (4.5g) flour, and remaining 1 1/2 teaspoons (3g) cinnamon. Stir in melted butter until well combined.
Punch down dough; turn out dough, and divide in half. Pat each half into an 8-inch square. Divide ginger mixture between squares. Using an offset spatula, spread ginger mixture onto dough, leaving a 1-inch border. Roll up dough, jelly roll style, pinching seams to seal. Place, seam side down, in prepared pans, and gently press into an even layer. Cover with plastic wrap, and let rise in a warm, draft-free place (75°F/24°C) until doubled in size, 40 minutes to 1 hour.
Preheat oven to 375°F (190°C).
Clean bowl of stand mixer and paddle attachment. Beat cream cheese, confectioners’ sugar, egg yolk, remaining 1/2 teaspoon (2g) vanilla, and remaining 1/4 teaspoon salt at medium speed until smooth. Spoon cream cheese mixture into a large piping bag; cut a ½-inch opening in tip. Set aside.
Using a small pastry brush, carefully brush tops of dough with egg white. Using a tight zigzag motion, pipe half of cream cheese mixture on top of one loaf, leaving a ¾- to 1-inch border; repeat with second loaf. (Retrace pattern on both loaves as needed until cream cheese mixture is gone.) Using a small offset spatula, spread half of Meyer Lemon Curd on top of cream cheese mixture on one loaf; repeat with second loaf. (Cream cheese and lemon curd layer will be thick.)
Bake until golden brown and an instant-read thermometer inserted in center registers at least 190°F (88°C), 30 to 35 minutes, loosely covering with foil to prevent excess browning, if necessary. Let cool in pans for 20 minutes. (Center will fall slightly as it cools.) Using excess parchment as handles, remove from pans, and let cool completely on a wire rack.
Place Simple Vanilla Glaze in a small piping bag; cut a ¼-inch opening in tip, and drizzle onto cooled loaves.