I have 2 cats, 2 Litter Boxes i clean them @ least once a day i try 2 times,my house smells like cat poo?

Any suggestions on how to eliminate the smell a bit more?
P.s I use this cat deoderizing powder too in the litter box.
Update: Yes i use a coverlitter box with a little kitty door too
Update 2: where can i buy The Worlds Best Kitty Litter?
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