Cost per Serving:
1. Make filling: Sprinkle gelatin over 1 Tbsp. lemon juice in a bowl. Set a sieve over a bowl. Mix remaining ingredients in a heavy saucepan. Place over medium-low heat and cook, stirring constantly, until thick enough to coat the back of a spoon, 7 to 10 minutes. Do not boil. Remove from heat; stir in gelatin until smooth. Strain into bowl. Discard solids. Cover bowl with plastic wrap, pressing onto surface. Chill until firm, at least 4 hours. (Can be made up to 5 days ahead. Keep chilled.)
2. Make cake: Place rack in lower third of oven; preheat to 375°F. Line a 15-by-10 1/2-inch rimmed baking sheet with parchment, allowing edges to hang over by 2 inches on short ends. Mist with cooking spray; dust with flour. Whisk flour, baking powder and salt to combine. In a large bowl, using an electric mixer on medium-high speed, beat eggs, sugar and extracts until thick, about 5 minutes. Sift half of flour mixture on top; gently fold in. Repeat with remaining flour mixture. Fold in buttermilk. Spread batter evenly on baking sheet. Bake until toothpick inserted into center comes out clean, 12 to 15 minutes. Remove to wire rack.
3. Run a knife around edges of cake; let cool 5 minutes. Sift 1 1/2 Tbsp. confectioners' sugar over cake; cover with a clean towel. Set a baking sheet on top of towel; invert cake onto towel. Remove sheet. Gently peel off parchment. Sprinkle cake with remaining confectioners' sugar. Trim crisp edges. Roll up cake with towel, starting from 1 short end. Place on a rack, seam-side down. Let cool for 15 minutes.
4. Make frosting: Using an electric mixer, beat butter and sugar on medium speed until light, about 1 minute. Scrape down bowl. With mixer on low, beat in cream cheese until no lumps remain, about 2 minutes. (Do not overbeat.) Stir in zest and vanilla.
5. Gently unroll cake. Spread with 1 cup filling, leaving a 1-inch border at 1 of the short ends. (You'll have filling left over; cover and chill.) Roll cake back up, starting at end with filling flush to edge. Transfer to platter, seam-side down. Spread frosting on all sides. Cover with plastic wrap; refrigerate for at least 1 hour. Let stand at room temperature for 15 minutes. Garnish with strawberries, if desired.