Prepare blistered tomato relish. Heat olive in in a large saute pan over medium-high heat. Add chopped onion and saute until softened and lightly browned, about 8 minutes.
Add red bell peppers and saute until softened, about 5 minutes. Add tomatoes and garlic and cook for another 5 minutes or until tomatoes begin to soften.
Add white wine vinegar and sugar, stirring to combine. Saute for 1 more minute and season relish with salt and pepper. Remove from heat and stir in parsley, basil, and balsamic vinegar. Set aside.
Prepare fried feta. Whisk together milk and flour in a medium bowl until well combined. Place panko in another medium bowl. Dip feta in milk and flour batter, shaking off the excess. Cover battered feta in panko, making sure to cover all sides.
Heat enough oil in a medium saute pan to cover the bottom over medium-high heat. Carefully lay feta in pan and cook until golden brown, about 2 minutes. Flip and cook until browned on the other side, about 2 minutes. Remove from heat and place on a wire rack or on a paper-towel lined plate to drain excess oil.
Assemble dish. Spoon tomato relish on a serving plate and place feta on top. Serve with crackers, crostini, or bread.
Notes
The blistered tomato relish can be prepared up to 3 days in advance.