To prepare cupcake, heat milk in microwave until just start boiling. Place tea bags in milk and let it steep for 30 minutes, and the mixture is at room temperature. Discard the tea bags.
Preheat over to 350F. Grease a loaf pan or a few mini muffin pans.
In a large bowl, sift flour, baking powder, baking soda and salt. Mix well and set aside.
Add sour cream and vanilla into the milk and tea mixture. Mix well and set aside.
In the bowl of an electric mixer fitted with the paddle attachment, mix canola oil and sugar on medium-high speed until well combined. Reduce the mixer speed to medium and slowly add eggs until just blended.
With the mixer on low, slowly add half the flour mixture; mix until just blended. Add the liquid mixture, mix until just blended. Slowly add remaining flour mixture, scraping down sides of the bowl with a spatula, as necessary, until just blended.
Pour batter evenly among prepared pan(s). Bake the cake for 30 minutes for a regular sized loaf or 20 minutes for mini loaves, or until a toothpick inserted into the center of the cake comes out clean. Let cool completely.
To prepare the glaze, mix lemon juice and the powdered sugar together, and whisk slowly until slightly thickened and pourable.
Spoon glaze over the cake(s) and decorate with edible rose petals if preferred.