Credit One has no grace period. If you've been using the card over the past few months and only been charged $2.15 interest to date, you're doing better than most.
A possible way to get Credit One report zero is using it at supermarkets and for gas for 1% back. Minimum interest charge is $1, so spend at least $100 on qualifying purchases and pay off the card within a week and it the reward credit will likely cover the interest cost. Another way is pushing payment of the amount due plus $1 (or a bit more, if you've been carrying a balance for awhile).
Be aware, paying off very quickly, especially if multiple times during a statement period, and/or often pushing excess payment could cause Credit One to suspend the account. No big loss, and may not happen. But something to be prepared for. On a related note, always check every statement (if none is mailed / emailed, login monthly) for trailing interest. Many used to having regular cards with grace periods get caught off-guard with Credit One, which charges interest from the date of purchase.
With all that said, while it's a big deal for some here, having most every account report $0 isn't a biggie. Just keep the proportion of accounts with balances under 50% or so. For one with only a few cards that can be challenging, but adding more accounts make it much easier (don't do that right now, since your sig says you've applied for a mortgage; wait until after closing).
