You could also add bits of sun dried tomatoes to the dough before adding the liquid. Remember, kneading scone dough will make the baked scones tough. Just pat out the dough lightly, cut and bake. Onions have sulfur compounds which are released when you cut into them. When these compounds drift up to your eyes, they mix with the moisture in your eyes and create sulfuric acid.
Some onions have more sulfur than others.
To win this war, I place my onions in the vegetable drawer of my refrigerator. When the onions are cold they release less of the sulfur. The coldness keeps the sulfur from evaporating as quickly. Vidalia, Walla Walla and Maui onions are the milder varieties. Some regular yellow onions are just so strong it is hard to control them.