In a large pot, melt 2 tablespoons of butter over medium heat. Add 1 chopped onion and sauté until it becomes translucent, about 5-7 minutes.

Stir in 3 tablespoons of flour and cook for 1 minute, stirring constantly to create a roux.

Gradually whisk in 4 cups of chicken broth and one 28-ounce can of crushed tomatoes, blending until smooth. Bring to a boil, then reduce to a simmer for about 10 minutes.

Add 1 tablespoon of sugar, salt, and black pepper. Stir well and let simmer for another 5 minutes.

Blend half of the soup using an immersion blender for a velvety texture.

Prepare the biscuit mix according to package instructions, folding in 1 cup of shredded cheddar cheese and the seasoning packet.

Drop spoonfuls of the batter into the simmering soup, cover, and cook for 15-20 minutes.

Melt an additional tablespoon of butter and mix it with remaining seasoning. Brush over dumplings before serving.