In a 12-inch skillet, melt 2 tablespoons (28 grams) unsalted butter over medium-high heat. Add corn, bell pepper, and garlic; cook, stirring frequently, until vegetables are tender, 4 to 6 minutes, adjusting heat as necessary to prevent excess browning. Transfer to a large bowl, spreading into as thin a layer as possible. Let cool to room temperature, about 30 minutes.

In the bowl of a stand mixer fitted with the paddle attachment, beat 1 cup (125 grams) flour, cornmeal, sugar, yeast, salt, and onion powder at medium-low speed until combined.

In a medium saucepan, heat ½ cup (120 grams) water, sour cream, and remaining ⅓ cup (76 grams) unsalted butter over medium heat until butter is melted and an instant-read thermometer registers 120°F (49°C) to 130°F (54°C). Add warm sour cream mixture to flour mixture; beat at medium-low speed until smooth and well combined, about 2 minutes, stopping to scrape sides of bowl. Add egg, dill, and remaining 1 cup (125 grams) flour; beat at low speed just until combined. Increase mixer speed to high, and beat for 2 minutes, stopping to scrape sides of bowl. (Mixture consistency will be a cross between a very thick cake batter and a very wet, slack dough.) Add cooled corn mixture; beat at low speed just until combined. Cover and let rise in a warm, draft-free place (75°F/24°C) until doubled in size, 40 minutes to 1 hour.

Spray a 12-cup muffin pan with cooking spray. Stir down batter, releasing as many air bubbles as possible. Divide batter among wells, filling up to ¼ inch from top rim (about 70 grams or a rounded ¼ cup each). (It’s OK if not all wells get filled.) Using lightly greased fingertips, smooth tops of batter into an even layer. Cover with a greased sheet of plastic wrap, and let rise in a warm, draft-free place (75°F/24°C) until puffed, 20 to 25 minutes.

Preheat oven to 350°F (180°C).

Bake until golden brown, 20 to 23 minutes. Let cool in pan on a wire rack for 5 minutes. Remove from pan. Brush tops with melted butter. Serve warm with softened salted butter, and garnish with dill, if desired.