Place potatoes in a saucepan, cover with water and bring to a boil over high heat. Reduce heat and simmer until tender, 10 to 12 minutes. Drain.

Meanwhile, heat 1 tablespoon oil in a large saucepan over medium-high heat. Add tilapia and scallops; cook, stirring once or twice, until just opaque, about 2 minutes. Transfer to a plate and cover with foil to keep warm.

Add the remaining 1 tablespoon oil and onion to the pan and stir to coat. Cover, reduce heat to medium-low and cook, stirring often, until lightly browned, 5 to 7 minutes. Uncover, increase heat to medium-high, add Italian (or poultry) seasoning, paprika to taste, salt and pepper; cook, stirring, until fragrant, about 30 seconds. Add wine, water and tomatoes; bring to a simmer. Reduce heat to maintain a simmer and cook, stirring often, until the onion is tender, 6 to 8 minutes. Add the fish, scallops, potatoes and capers (if using), return to a simmer and cook until heated through, about 2 minutes. Garnish with parsley, if desired.

Note: Be sure to request "dry" scallops (i.e., not treated with sodium tripolyphosphate, or STP) from your fish store. Sea scallops that have been subjected to a chemical bath are not only mushy and less flavorful, but will not brown properly.