Sinceriously

And Widow put hand on either hip, and Mephistophelied up her left eyebrow - I needn't say that her hat came down in sharp tune - and eyeing me very sinceriously, she sang solemnly, for several minutes:

Source: wiktionary

"I most sinceriously hope, dear lady, that this problem may be resolved without any such unfortunate occurrence," said Rozanov. "Might you spare me a few moments, Mr. Redmond?"

Source: wiktionary

"You have no idea what he wants, Katiebear. That's what I'm saying. If he sinceriously wants to work something out, don't you want to?"

Source: wiktionary