In a medium bowl, break up the drained tuna with a fork.

Mix in the chopped roasted red pepper, chopped onion, mayonnaise, olive oil, paprika, lemon juice, salt, and pepper.

Adjust the amount of mayonnaise to achieve a thick consistency.

Lay out 4 slices of sun-dried tomato bread.

Top each slice with 1/4 of the aged gouda cheese.

Spoon the tuna mixture onto the cheese-topped bread.

Cover with the remaining bread slices.

Brush the outside of the sandwiches lightly with olive oil.

Heat a heavy nonstick skillet over medium-high heat.

Add the sandwiches to the skillet (in batches if necessary).

Weight the sandwiches down with the bottom of a heavy frying pan to keep them flat and help the cheese melt evenly.

Reduce heat to medium.

Cook on the first side until the bread is crisp and golden brown.

Turn the sandwiches over and repeat the cooking process on the other side.

Check on the cheese occasionally to ensure it melts completely. Remove from pan when the bread is golden and crisp, and a little cheese has oozed out.

If the bread is browning too quickly before the cheese melts, reduce the heat further.